Hello!
In such a situation I'd use a piece of wire and insert it into the mounting hole (make a U-shaped holder, if there are two of them), the plus side is you can later use the same wire as hanger for drying. If there are no holes and I don't want to make any, I'd take a piece of stretched sprue and glue it to the painted object with CA, so that after painting I can snap the holder off. The attachment point has to be chosen so that it will be masked by a pylon or something, so that I don't have to touch it up. You can use the regular sized side of the sprue as a handle and the small diameter, stretched end as the attachment point. Hope it helps, have a nice day
Paweł