I've done it by partially seating the bullets of a batch in a loading block and then putting it on top of the running clothes dryer for 10 or fifteen minutes. Then the bullets can be fully seated.
I've also done it by charging the cases in a loading block and placing a piece of flat plastic on top. Big rubber bands hold the covering plate in place again for 10 or 15 minutes on top of the dryer. Seating the bullets as normal afterwards.
