Unfortunately, it appears that he could have done better had he addressed the entirety of the Decree on Justification, rather than cherry-picking quotations that seem to better suit his purpose. I've already addressed this problem in another post or two (and, to be fair, Turretinfan isn't making an uncommon error in this respect: many Protestants do so). As I said then, we can't understand the decree apart from chapter 7: What the justification of the impious is, and what are the causes thereof. But Turretinfan has omitted any discussion of this fundamental part of the decree.
It seems reasonable to me - given the title of that chapter, that it ought to be of paramount importance in any consideration of the meaning of the decree as a whole. It seems to me that if we're going to talk about what Trent's views were on how we are justified, then perhaps the most important stuff to consider would be those passages wherein they discuss the causes of our justification. And if we do that, we will see that chapter 7, in which the causes of our justication are declared, gives no place whatsoever to human works or merits as a cause of our salvation. Read it yourself. See my discussion of it here.
Now, that being the case, an inescapable conclusion is that for Trent, any human activity with respect to our justification is not actually a cause of it, but rather an effect of God's grace. Yes? No? If Trent specifies the causes of our justification, and none of them are human merit or action, then how on earth can it reasonably be said that Trent denies sola gratia? This makes no sense.
If all this is the case, then what must we conclude about passages in Trent that address human merits or activity with respect to our justification? Well, as I just said, we must accept the fact that such things are and can only be effects of God's grace and consequently not causes of our justification. We must realize then that in rewarding these merits, which we receive from Christ, God is only blessing his own good gifts. See here.
So - with all due respect to Turretinfan - I do not think he has adequately addressed the substance of what Trent teaches about our justification. He has ignored the fundamental context, and consequently has misunderstood the Decree.
Perhaps a bit more ought to be said. It's my understanding that the Fathers at Trent brought with them two things to the Council: Scripture and the Summa Theologica of St. Thomas Aquinas. It's rather more than I would like to put into a single post here, but it simply cannot be denied that St. Thomas affirmed the necessity of grace from start to finish for us. If, as he taught, neither Adam in his unfallen state nor even the holy angels themselves could see God apart from his grace, then it is flatly absurd to suggest that fallen man could ever do anything in any way to merit any good thing from God. Indeed, since St. Thomas understands God as the First Cause, it's irrational even to suggest. Now I certainly don't mean to say that the Fathers at Trent would have held his works to be on the same level as the Scriptures or Sacred Tradition, but if his work - as an explanation of Catholic teaching - was considered to be so valuable to them, I would suggest that his views would be an indispensable tool in understanding what the Council taught. In this case the consistency is clear: St. Thomas affirmed sola gratia, and so does the Council of Trent.
With respect to the two Catholic scholars mentioned by Turretinfan in defense of his view of Trent: I'm not so sure that they demonstrate what Turentinfan wants. Dr. Seifert doesn't even mention Trent. What he does do is contrast the Protestant notions of sola fide and sola gratia with the Catholic position. But I have done the same: I say that Turretinfan is simply mistaken when he claims the only legitimate construction of sola gratia is the Protestant one, in which there is no place for human action as an effect of God's grace. But to deny a Protestant construction is not the same as to deny any formulation of the idea whatsoever.
The same may be said with respect to the article by Dr. Marshner. At the very outset he identifies and distinguishes a Protestant notion of sola gratia as different from a Catholic one, thanks to a different understanding of what exactly grace is:
neither the apparent agreements nor the apparent disagreements can be understood without looking at certain metaphysical quarrels, the chief of which is over the very existence of what Catholics call "grace."Dr. Marshner concludes his article thus:
Living faith: our quality but God’s instrument; good works: our deeds but God’s handiwork; our deeds as men living in Christ, not the motions of "graced" zombies still dead in sin—these are the possibilities overlooked by Luther and Calvin but preached by Paul and defined by Trent.I'd have to say that this sounds suspiciously like what I've been saying above (and elsewhere), not like (pace Turretinfan) a flat denial of sola gratia. Our good deeds are an effect of God's grace: they are his handiwork, to use Dr. Marshner's word drawn from Ephesians 2.
Far from having demonstrated that Trent denied sola gratia, all Turretinfan has really done is show that Trent rejects a Protestant construction of the idea. That should be unsurprising :-) Either he has not read the whole of the Decree, or else he has misunderstood the significance of the 7th chapter for one's understanding of the whole, and instead views the Decree through his Protestant lenses. He sees the Protestant idea rejected, and concludes that the entire thing must be. But this is not a necessary conclusion at all, and given the context of the whole Decree it seems not just unnecessary but invalid.
[Update] Turretinfan has added a qualification to his post clarifying what he means by sola gratia. This is a welcome amendment, and I thank him for it. I would still be interested in how he thinks chapter 7 of the decree affects his presentation of what Trent says on the subject.