Punches work well for me when I have a small ring gauge cigar or one with a very minimalistic head.......other times I use a DBG. The trick to a DBG is to get the blades right up to where they touch the cigar, and then give a quick, yet powerful close of the handles. If the DBG is worth anything at all, and sharp, this method should leave you with a nice clean cut.

Whatever you do, stay away from single bladed guillotines......