I\'m not sure how new you are, so if I mention something you\'re already aware of, my apologies.
My first question would actually be are you putting primer on your models before you paint them. Spray or brush on doesn\'t matter, and there are a lot of different brands that people use. But primer is designed to stick to metal, and paint to primer, so if you\'re painting straight onto the metal (or using spray paint rather than spray primer to prep the mini), that can cause problems with paint rubbing off.
Also on the subject of prep, it\'s a good idea to wash your mini prior to priming it. Moulds for miniatures are prepared with a light dusting of talc or a similar release agent, and when you\'ve been handling your mini preparing it for paint, you\'ve been getting oils from your skin on it, both of which can cause paint not to stick as well as you might like.
Another suggestion is to mount your miniature on a holder so you don\'t touch it a lot while you\'re painting. You can glue or poster tack it down to a spare bottle of paint, a bottle cap, people use a hundred different things for this depending on the size of your hands and what you have around the house.
The Dullcote people have mentioned is a matte finish made by Testors. It comes in a brush on format, but that requires a special thinner, so most people use the spray. If you can\'t find that, look for Krylon or other craft matte sealer sprays in a craft store. Reaper makes a water-based brush on sealer in their Master Series paint line. Thin it about 3:2 sealer:water for a matte finish, use it straight for a satin finish. Gloss sealer is more protective, so if your mini is for gaming, you might want to get a gloss spray sealer as well. Spray the gloss first for protection, then the matte spray to kill the shine.