My advice? Don't assume you HAVE to prune them. Neither andromeda nor azalea particularly needs pruning -- and both are often pruned BADLY. The look a little drab after blooming because, well, they're done blooming. Once the spent flowers fall off and the new growth begins, they'll look fine (although azaleas just aren't all that attractive other than when they're blooming which is one of the many reasons I think people are nuts when they plant nothing but azaleas in their home landscapes). Especially if you're new to this property and these plants, I strongly suggest that you just leave them alone for a season or two.