Hello! I'm not new to Kirby games, but mixing was something I've never been good at. It's something that actually kept me from running KSS way back when, because I just couldn't figure it out. Are there any tips or something to help get the ability (Bird, in this case) you want?
First, you should know the order of each ability on the mix wheel, because it's always the same. For example, Wing is always proceeded by, Sleep, then Festival, then Sword. Once you know that, wait for the roulette to slow down. Then hit the home button when it approaches the ability you want. Once you get close, hit the A button depending on how close you are. It'll take some practice but once you get a feel for it, you get it most of the time.
If you do light mashes on the home button until Festival, you can use the audio cue from sword to time the A press and get the roulette to stop 2 forward on wing. That's what I do. But you can fast mash from Sword to get the same result. Definitely requires practice. I recommend going to level 1, going to where kibble is next to the fire guy and bomb in the third room. Run up to kibble and shield boost him forward, mix, then try to get wing as often as you can. You have 3 cycles of the roulette to get wing before you pass it and get a random power from the wheel. After you mix, run left to halfway up the slope and then run back and repeat. This is faster for PRACTICE than the any% method we use with 2 double shield boosts in room two to get kibble next to the knight.