You'll want to trim them fairly thin. Here is a barnacle murrini chip next to a regular murrini chip:
If you make them thin, they will be less likely to draw inward on themselves.
To use: Heat the spot on the bead where you want it to go, press it on (after preheating on your torch marver or on top of your kiln), heat and press it on gently with your marver. Reheat and voila!