Pro-Tip: Brushes.

Use decent brushes. Try a ton of brushes. No, a Winsor Newton #7 wont make you a "pro-painter", but it sure helps getting those fine lines fine.

Don't throw away old brushes. Use them to basecoat, mix paints, delegate them to dry-brush work, use them as mixing sticks… Just don't do detailing with them when the tips start to hook or fray and wonder why your paintjob looks like crap.

Use different brushes for metallics! Nothing sucks more than to see mica crystals in your non metallic paints.

From left to right: Winsor Newton #7 sz. 0 & 000. Citadel Standard & Fine Detail. Citadel Standard & Fine Detail for metallics. 2 crappy Vallejo brushes used for oil based stuff. Old Citadel Standard, used for paint mixing. 2 soft bristle "art" brushes. For oil based stuff and basecoating larger stuff. Old red GW drybrush. GW small drybrush. GW stippling brush (yeah I know), 3 GW drybrushes in various stages of decline. Army Painter small drybrush. Crappy Vallejo set-brush. Huge GW drybrush.