If you need to "scrape" and it's a teflon platen. I let my press cool so it above warm (versus piping hot) and spray with Simple Green and gently "scrape" with heat resistent silicone spatula from the kitchen. I wipe with old t-shirt.
If aluminum platen...you may oxidize your platen by cleaning with steel wool....info shared from another board.
Also, I really love Reynold's Baking Parchment Paper. Not only in lieu of a teflon sheet (which I have) but what I do is place a sheet down and gently lower my upper platen and wiggle over the parchment paper.
I have a swing press. I then lift and see if there's any residue on the parchment paper. Then I do a visual inspection and wipe down again.
It really is not fun when you go to press your next shirt and you get residual
transfer on a new blank.
This happened a few times with the Hanes "Tagless" t-shirts. That "Tagless" information does melt and get on your upper heat platen.

I try to not make the same mistake twice.
Welcome to the heat press world!