painting smaller 1/72 detail parts

I assume you mean small parts that are molded onto larger parts and not small parts that you could paint separately before they are glued in place.

For cockpit and wheel well wiring on airplanes, which is also usually molded in place, I usually use a number 20/0 spotter brush (available at most art supply stores) and paint that is somewhat on the thin side. Start painting in an area away from where the mold line joins, and then use the end of brush to push paint toward the joint. That works better for me than just pulling the brush along the part, but it does get tedious when the areas are very long. If you make a mistake and go over the line, just let the paint dry thoroughly and then touch things up with your base color.

For tires and wheels I usually airbrush the lighter color (normally the silver on the wheels) and then hand paint the darker color. Use pretty thin paint and it will usually run down into the groove between the wheel and tire.

There are liquid masking agents but they have to be painted on as well. If I'm going to paint them on I might just as well paint the color instead. Besides, most of them don't work well on acrylics and that's what most of my painting is done with.

QUOTE: 2). wheels with tires on them. need to paint the rim itself one color but the tire black or some variation thereof. i usually end up setting the wheel on a toothpick and rotating it with the brush up on the side of the tire. This isn't as neat as i'd like. masking solution?

For this one, get a flat lid bigger then the wheel.
pour paint in the lid so that it reaches the edge of the wheel rim,but not the rim itself.
now roll the wheel in the paint, instead of the brush method.

I'd echo MusicCity's suggestion, as I've have better control with a paint brush. Frequently, aircraft canopy decking has the molded-in detail that I think were talking about. When I have to paint a large molded-in detai area, I use a No.4 flat brush and "dry brush" the details. When I have smaller area or one or two to pick out, I use the No. 18/0 spotter.

For wheel/tire combos, I've had pretty good luck with painting the wheel first, then chuckin' the assembly on my dremel tool, run it at low speed, and hold a brush full of tire color paint against it to paint the tire.

Normally, the only time this is problematic is when the wheel is very out of round.

Also use this to sand tires down to get rid of molding seams or if they are vinyl, to add some "wear" to the tread. Old slot car/model car trick from years back....(anybody remember the "Auto World" catalogs???...)

If you can mix your paint types, wheel color acrylic, tire color solvent based, (or vice-versa) cleaning up mistakes is pretty easy, as the cleaning agents don't harm the underlying color as easily.

I get good results with a really small paint brush (No.0) and using a magnifier light to allow me to really see what I am doing.

For wheels, I actually leave them on the sprue for painting, again using a small brush to do the area right next to the rim. Since I usually paint my models with enamel, I paint the tires with acrylic black, which enables me to wipe off mistakes more easily.

Another thing that you can do to fix mistakes, is use a new no.11 exacto blade to cut of any paint that went onto the hull.