To fit the crown race I use an old Klein hairset bearing, I put it on the crown race and gently tap it with a rubber mallet, using a screwdriver. It sounds like a sure way to index the crown race but it has always worked (and I substitute the crown race quite often because I frequently change from rigid to suspension forks).
However, sliding a tube of the same size of the crown race on the steerer and use it to tap the crown race itself is probably safer.