hey to answer your question. i just finished out my first tin of resin, and it had enough in one tin to resin everything except the chest(still assembling) and codpiece(spellng?)(you know the part that goes over your butt and crotch, just finished it) and it let me fiberglass the inside of fore-arms, hand guards, biceps, and feet. so im gonna ballpark at 2 tins, though if your sloppy at resin-ing and fiberglassing like me then you might have to go get a third. just buy them one at a time, wal-marts open 24hrs, so just run up there every time you run out.
and good job, you seem to be way faster at assembling the pepakura than me....its the longest part of the assembly....well, besides fiberglassing each piece, which is a close second.