I tried upholstery spray paint years ago with pretty good results, and I've been wanted to try painting upholstery with a brush for a while too. I got a pair of little white swivel club chairs a few months ago for $30 for the pair. I love the shape of the arms, but the fabric was pretty dingy and old. I knew I would want to reupholster these eventually, but I didn't know what room they'd go in and I wanted to wait to choose a color/pattern. These felt like the perfect candidate for painting the upholstery.
I followed these instructions and used textile medium and Valspar paint from Lowes which is actually acrylic paint. The color I chose was Sunburst Orange from Benjamin Moore. It's a bright, fun coral that's perfect for accent chairs.
The basic idea is you mix textile medium with really, really watered down acrylic paint (so you can buy craft paint if you don't have a huge surface area to cover like I did with two chairs). You spray the upholstery with a water bottle and then softly brush on the paint mixture.
You have to do several coats with drying time in between and you sort of have to find that sweet spot of even coverage and not too crispy from the paint. These chairs are a little stiff, but if you use a sanding block to knock off any uneven bumps and to loosen up the paint a little, it ends up feeling sort of like canvas. Not exactly like silk velvet, but not too bad.
I wouldn't do this with special chairs that you're going to sit in all the time or a primary use sofa, but it's a perfect option for accent chairs or (and maybe especially!) dining chair seats.
Have you tried painting any of your upholstery? How did it work out for you? I'd love to see any links if you've posted about it.