I’ve got reasonable experience with it, but nowhere near pro level. I’ll fix things in my house, though I don’t like the painting part. It’s just… it takes longer than I want it to, so small jobs suck. Big jobs are fine, because you do all the first-pass things, then come back for second pass without having to wait too much.
Anyway, here are some things that come to mind when I think about doing this.
0. Preparation! Scrape, clean, and mask the area with twice as much effort as you think it deserves. Also, um, those clothes that “you probably won’t get anything on” will totally have splatters.
1. Don’t be afraid to peel back some of the paper backing to keep it from being humped too high.
2. Finding a way to do the inside of the wall when it’s a big patch is really helpful for stability. Strings tied around things can help press from the inside, and hang a weight on the outside. You can also mount a support (paper tape, mesh tape, wood strips, whatever as appropriate. Don’t just mount tree branches in there though) inside of a large hole (can you fit your hand and a putty knife through the hole?), and let it dry, then use that as backing when you come back to put in the plug.
3. Fiberglass mesh tape is sometimes so much better than paper tape. It’s strings! It takes several coats to cover up though.
4. Once it looks dry-ish, stop messing with it. Once it starts peeling up or crumbling, you really just have to scrape it all out and start over. You can spritz it with water before and during to keep it from drying too fast if needed.
5. Sometimes you have to do a little, let it dry for half a day, then come back for the next part. There are limits to how much can be done at once and not have it crack.
6. Use as wide of a putty knife as you can. If you have a 3mm hump spread over 2″, you will notice it. If it’s spread over 6″, maybe not. I have a 12″ mud knife, and have actually used it before.
7. Texture often needs to be thinned. Paint works better than pure water for this, because it’s sticky, and not as thin. 50% paint+texture is a good starting point for a crow’s foot brush.
8. Overlapping is your friend. When spraying orange peel texture, I start small, and adjust until the blob sizes look just a little smaller than I want. Then, I go back and forth, overlapping the edges, until I cannot see the true edge anymore.