Since you've posted this in the color section, I assume you're referring to color printing. So you have to be conscious of unhealthy fumes, which would make a big open trough processor a bad option. You can use big sections of black ABS plastic irrigation to make your own processing drums. These can be loaded in the dark then even taken outside to a sidewalk or whatever and simply rolled back and forth. But with a bit of imagination, you can build a roller processor base using drive rods and a low RPM gearmotor. My own color drum processor handles up to 30X40,
and is mounted onto a cart which I push outdoors during good weather.