I have used a 10# short sledge hammer on the cups, a rubber mallet, a block of wood supporting the cups with a 5# hammer driving the cups in, and a cheezy romance novel protecting the cups when I bang on them with a BFH. (big f-ucking hammer)
I've installed many a headset this way, and I've never had a problem. Installiong a headset was the easiest thing that I've done on my bikes.
In fact, when I worked at a shady LBS, we used many of these DIY methods.