Here you see stage one. I fix a Nut to the underside of the miniature I'm working on using superglue. I have to emphasise here not to use too much glue. I put 5 tiny dots of superglue on the bolt then placed it in position. This is enough to hold the bolt to the miniature but provides a weak enough bond that the nut can be snapped off when finished without damaging the model.
With the nut affixed to the model, and the glue dry, I then screw in the bolt. Don't over tighten as this could snap the nut off the model or even damaged the miniature itself. I have found that this arrangement is more than strong enough to provide a stable 'handle' on the model without being too intrusive (unlike blue tack which needs a large surface area of contact to provide a similar strength bond). As has already been mentioned, when finished the nut & bolt 'handle' should snap off easily without damaging the model - provided you glued it into place sparingly. I have a wooden 'drying rack' consisting a series of holes drilled into a piece of wood. When I need to stop painting to allow paint to dry I put the bolt into the hole and it holds the model securely in the air and, crucially, untouched by any surface (which might blemish the drying paint).