I'm probably the only one at the time that didn't know the secret. I did "win" a few packs of the winner cards on my own, but it stung a bit when my friend showed me the flashlight trick.
Didn't matter, all Topps sent me in return was a bunch of bums. Not a Ripken, Thomas, Manny Ramirez. No, it...
GIMP is a desktop app, available for Linux/Windows/Mac.
https://www.gimp.org/
As for printing, I use card stock with my printer at home. A little more expensive than plain paper, but it does the job.