It's very, very quiet in here - Shhh!
Anyway, I finally got my platinum tonight. Yay!
It was much easier than I thought. I farmed for 2 more ingots (and got them pretty quickly) The hard part was actually killing the 'toise - had to restart like 4 times in a row because Death never worked. But I killed 3 and got 2 ingots and 1 Trap. It's almost like I've gotten much better drop rates since I maxed everything out - I wonder if the game is more forgiving at that point? Early on, and maybe it was even before I finished the game though I'm not sure about that, it seemed like I only got a drop every 5-10 kills. Toniight and the last couple of times I farmed, I got something nearly every time.
Anyway, it turned out I didn't even really need them. Here's a tip - if you haven't been selling stuff all along, you probably have WAY more stuff than you need. Once you get to a point where you've maxed the characters and 5-starred all the missions you can go for broke and sell off everything and do the upgrades all at once. I wanted to make sure I could do it so I made my cutoff point when I upgraded all the accessories, and then all the regular weapons to Tier 2 (besides the 3 Tier 3's I made a long time ago).
So, basically, I did everything except the Gilgamesh ~200K weapons, and then 3 Trap upgrades for the characters I didn't use very much (Snow, Hope, and Sahz). And it turned out to be much easier than I thought so I probably could have done this at least 3-4 hours back (and done less farming). I didn't even sell everything off and didn't touch any of my upgraded weapons (to sell that is). I pretty much just did it by selling off extra accessories and some big ones like the Growth Egg and an Imperial Armlet or two. My main save (if there is ever a need to come back to it like DLC or something) will be before these last-ditch upgrades. I just wanted to get that last trophy out of the way.
So, anyway, the point is you can probably sell everything off and purchase the rest of the upgrade stuff at a much earlier point and save yourself a lot of time. I'd say give it a try as soon as you get enough Traps to do whatever weapons are left over. Of course, you just have to be thorough and make sure you've done all the upgrades before you sell something off. I made sure to do all the accessories before the weapons so I was safe selling anything from there.