Miniatures are small.
So it's no surprise that you might think that painting miniatures would be a nearly impossible task. I have poor eyesight, and terrible eye-hand coordination. My hands tend to shake, I usually have an abundance of nervous energy, and my depth perception isn't amazing. And yet, I'm painting miniatures.
The trick is that you don't actually "paint" miniatures. Painting miniatures is actually a 3d colouring-in book.
If you're imagining Da Vinci or Van Gogh standing before a canvas, waving a brush mystically to unveil previously unseen images, then you're on the wrong track. That's not what miniature painting is, or at least it doesn't have to be. Sure, sometimes you get a proper brush stroke in, but "painting" a miniature involves a lot more osmosis than I'd realised.
It works like this: You dip just the very tip of your brush in the paint pot, then you hold your brush close to the spot on the miniature you want to colour in. You keep holding the brush close, and closer, and closer, until suddenly the paint isn't on the brush any more. It's on the miniature.
That's my technique for a good 88% of my painting. I don't know whether it's right or wrong, but it's what works for me. I hold the brush near my miniature, and the paint spreads onto the region I want to paint. And because the model is 3d, there are lots of ridges and dips in the surface of the miniature, so the paint that I nudge onto it usually stays where I intend it to go.
For instance, one time I had to paint some leather straps of a backpack. On my first try, I tried to paint Bugman's Glow (that's the name of the brown I was using. I told you, I just use paints with cool names and it comes out great.) paint on the strap. Paint went everywhere. All over the chest plate, all over the shoulders, on the head. So I waited for it to dry, and then painted over the mistake. No big deal. Mistakes happen, you just cover them up with more paint.
The next model, I discovered my paint-nudge trick. Instead of moving the paintbrush over the model as if I was painting a canvas, I just gave the miniature a light touch with the tip of the paintbrush. The brown paint's surface tension released, and Bugman's Glow poured off the brush along the strap, and it even stayed within the lines of the strap. This has been my go-to trick ever since.
I have since learned another trick from a master painter at my local Warhammer store. It's the "flick" or "fly-by" method.
You probably think of painting as pointing a brush at something, and then pressing down. That works on broad surfaces, but it's rubbish when you're painting a badge that's a 2mm square on the shoulder of a 28mm Traitor Marine. Instead, you make your brush fly by your target. You just nick it with a little paint off the glancing side of the brush. It's a little tricky and does take some practise, but you get the hang of it eventually, and it's a great way to hit tiny targets with some incidental colour.
Literally, less paint is usually better than more paint when it comes to tiny little 28mm models. You can't imagine how little paint you actually use for a miniature. Sometimes I scold myself for using "too much" paint when I have to cover up a mistake. Then I look at the tiny droplet of paint on my tiny brush, and compare it to the several liquid ounces of paint in the pot, and realise my sense of proportion is grossly maladjusted.
Less is more, because those miniatures are small. Use a little paint. It's easier to control, and it goes farther than you think.
If the idea of you painting scares you, don't think of what you're doing as painting. Think of it as transferring really small amounts of paint from a pot onto a model. This is easier than "actual" painting. By the time you've gotten good enough to realise you are actually a skilled painter, you'll be good enough to be able to pull off the humble-brag "who me? I'm not a real painter, I just paint toy soldiers for fun."
T'au soldiers photo by Seth Kenlon. Creative Commons cc0.