We've got a collection of cheap mug presses, and do fine on them, one of them though I've recently put to use for preheating mug bases before printing it's set to 100 degrees C, and being a horizontal press, I can slide in two mugs, one at each end, with mainly just the bases actually in the press - it isn't set tight, so can easily slide the mugs in and out - so I have two presses running for printing, and this one preheating the next two mugs. This works well for the moment, but will be looking an electric hot plate of some kind to take over, as I can print mugs quicker with 3 presses running properly!
Edit to add - came to this idea when trying to print up a batch of glass mugs, where it's best to preheat them otherwise they crack (rather than a print quality issue) doing this stopped them cracking 100%, whereas without preheating, it seemed to be 50/50 whether they'd survive! I kept using this method for preheating ceramic mugs and the print consistency was a lot higher than without preheating.