I did Kaplan prep, so angle ranking kicked my ass on the actual test; but I would narrow it down to the largest and smallest, and then if the middle two are very close, I'd use my thumbs to cover up only but the most inner part of the angles so it makes them look like they have equal length legs. They say not to touch the screen, so just kinda hover a bit. It's not the best method in the world, but I ended up using it on a few and it helped.
Otherwise, I'd say to get CrackPAT!
Good luck!