Hold shield at any time during the ASC. It should shield cancel automatically
Not really, you have to be holding it when you land lol.
Do you have any tips on learning how to do advanced techniques like the spinshot and the ASC shield cancel and how to get accustomed to using them in your general playing? I'm having trouble getting the timing down on the spinshot and I never cancel the ASC... I never use the side-b spin dash either, and apparently it's better to use in certain situations...
Also, do you have any tips on how to accustom yourself to using tilts (mainly f-tilt and u-tilt) instead of smashes? I can't get myself to stop using the f-smash as a punish when the tilts are said to be better. I always end up u-smashing instead of tilting if I ever try to u-tilt..
Spinshot (general usage) is almost all timing. If you're using a GC controller, try practicing it by holding side-B for a while, then quickly sliding from B to A.
A common problem is that you might try to be doing it too early, but remember there's start up lag, so holding it might fix that. If you just double jump slowly, then hit A earlier. If you jump straight up, then you're hitting A too quickly.
Keep in mind you can also use jump, up, or some other attack button (c-stick, etc)
ASC shield cancel - just release an ASC and hold shield. That's all there is to it. It'll stop and turn into a shield as soon as you land.
Side-B is more of a utility move than anything. If you're in a 'rhythm' while you're fighting a human opponent, they'll get used to "oh, I'll just tap shield when he comes by then punish him later" or "I'll just time it so I can grab him" or "I'll spotdodge his move", then just run at him and tap a side-B, and it'll throw him off.
Side-B can also be used to make you look vulnerable when you're really not. An example is to stand outside of his forward roll range and charge for like, .5-1 second and see if your opponent does something like roll forwards (shield cancel it and grab him) or try to attack you (shield cancel and attack), or some other weird movement.
Try walking. It'll help you a ton with tilts. You might be playing really rushed and so you tap the control stick and don't tilt enough.