Bill-
Not really, just a little patience. I carefully snip them from the casting block (many are attached to the block at the crest of the helmet) with a pair of tiny jeweler's scissors. I shave off, what I can, the remnants of the block with a brand new #11 blade, then sand them down. Most always, there will be tiny air holes at the point where the helmet met the casting block. Enlarge them by spinning the blade tip in it, to clear out them out. Fill in with putty, let set. Sand down the putty, make uniform and smooth with 600 grit sandpaper. Ready to go.
Don't forget to add chin straps, if not molded on. Prime 'em like anything else.
Some manufacturers give you a lot of neck... I whittle down what I don't need.
Resin heads are definitely the way to go. Hornet is outstanding, Warriors are great, Tahk, amazing.
Personally, I don't like Verlinden, and I find some manufacturers' heads too small- Aires, Legend...
Hope that helps out,
Steve