Agreed on the press, I assume every prospect is gonna struggle with press more than anything, unless they give me concrete evidence(which is kinda rare), so I always factor that in with WRs lol
there's things prospects do when they release that can give you clues - obviously if they never line up outside you're just never going to see any reps that remotely look like it - but there are guys who line up outside but dont get physically pressed (more soft-pressed) and how they release tells you a lot about what they might be able to do
dwayne eskridge was one of the few smaller faster guys who faced press on the tape i watched - and while it wasnt always perfect i saw him using his 2-way-go to create room to release, and i saw him using his hands to swat away the corner's hands to protect his chest - now the issue with eskridge is that the level of competition is lower (which is why this senior bowl week will be massive for him - and if he shows out i think he's going to skyrocket up a lot of people's boards)
but yeah with the guys you dont get to see that on tape - im looking for traits physically that suggest they can deal with press or route running savvy that suggests that they already have in their brain that idea of how to release to out-leverage a corner...
but you're right that it's so rare to find concrete evidence
now the problem i have is when you do have a ton of reps but the prospect does poorly consistently - now does the inability to get off the line of scrimmage (and generally just run routes) push them down the board below guys who've not been pressed at all? that's the difficulty i have and specifically with 1 prospect in particular who was consistently pressed out of the play on tape