Yes, spring is a great time. As soon as the soil is workable is the best. I've found that the best way is to dig them up and then put two spading forks side-by-side in the center of the clump. Push the two handles of the spading forks together so that the center of the clump splits in half. The roots of one will stay with the clump it's supposed to stay with, and the roots of the other will stay with the clump IT'S supposed to stay with. Also a good method for separating hostas.