Exactly what it says, honest.

Make any sort of print (including mini-lab from film).

Make a colour Xerox of it (ideally flopped -- or flop the original -- because the transfer will of course be reversed left for right). Many public libraries have colour Xerox machines nowadays.

Soak the colour Xerox in solvent.

Burnish down onto water-colour paper (or anything else, really) with the back of a spoon.

Cheers,

R