Depends on what you have laying around and how much you want them to look factory. Keep in mind they are always fully hidden when the car is done.
The dash is pretty easy to get a backing block and peen the surface. A good hit with the right hammer (it is good to have a collection of odd hammers).
A big C clamp and ball bearing can work too supposedly.
If you have two people, one can back the nut while the other holds a large ball bearing (pinball works and I have lots of them) and wacks it.
You could just tack them in place with a welder too. Just be sure they are below the metal. I did this on a couple since it was just easiest to do without help I did not have at the moment.
Lots of good solutions, you are only limited by resources and creativity.