I finally have a comfortable system for mounting my miniatures while painting them. I have tried mounting with sticky gums, but this leave a residue and/or can be a bugger to get off. I have tried glueing with PVA, but adhesion is too weak and ended with models flying off into the grass as I spray primed them. I have tried using hot glue, but adhesion is too strong and ended with several broken legs while detaching the models.
In the end I settled on using 3M's 1/2" Double Sided Mounting Tape Squares and soda bottle caps. The squares are right sized, precut, many (90 per pack), cheap, and hold the model firmly.
Here are my current steps to mounting and priming.