The sealed switches sound like good idea for the plastic dip.

I've done the heat shrink before with good success. If the button gets depressed by the tubing a quick cut with a craft / xacto knife around the button works well.

I'm not trying to make it water proof, just survive being banged around by all the pens / keys / USB / cables / power blocks / change / assorted other detritus that lives in the pockets of my computer bag.