For those in the UK (as I've never heard of acetone) brake fluid is perfect. Soak metal miniatures overnight in a large glass jar (it won't corrode and with a seal-able lid will last ages). Once the morning comes brush off the paint with an old toothbrush*, give a good wash in soap and water and marvel at your 'new' miniature. £5 for a couple of litres of brake fluid and it is entirely reusable, I've stripped thirty or so large metal minis and the 400ml of fluid just keeps stripping (although I wouldn't want to spill it on the carpet).
For plastic I've used 'dettol' and it's worked well when submerged for 10 minutes, then give it a good brush off with an old toothbrush *or in my case a clean old shoe brush.
Another stripping agent I like is PineSol (a pine oil based floor cleaner). It works well overnight, I have even used it on plastic minis (much shorter time).
Barton Stano
GameMaster of Pulp RPG using Hero System
Rat Rancher (rat ranching had better be fun, it sure ain't profitable)
learning to paint and sculpt
Lombard, IL USA