I made my own processor once & it worked pretty well for a simple gadget

it was just a pair of polaroid rollers attached to a board with alignment pegs to keep the film together & a jig to keep the chemical packet thingy in place

ya had to connect the end of the film to the strip of plastic in the chemical packet thingy....smush down & pop the chemical packet.....then ( in the dark ) gradually draw the film & plastic backing slowly through the rollers

after the required time, just peel apart