Runemist, I had the same problem when I first started filming and I still know I'm not as smooth or fluid or strong or sexy as so many people here. I still cringe when I see myself going into weird wrist-flicky gymnastics hands. But anyway, these are a few things that help me.
1. Don't worry about the camera for new moves because they'll look awkward, and it's important for you to learn the feel of them. Filming is best for moves you're confident with to improve your lines and smoothness. So film stuff you can already do confidently.
2. Start by filming a short combo, watch it back, and then delete it. Try to find one thing to improve for the next time. For me this is usually the aforementioned wrist flicking, but it could be pointed toes, more/less hip turnout, not pulling a face, etc. Then film the combo again, see if you improved that thing and delete. You can keep deleting until you get something you're happy with.
3. That said, if you can stand to keep a few early attempts they can be useful to look back on and see how far you've come. If you keep filming you can really notice your improvement.
4. Every time you film, find at least one thing that you think you did well, or better than last time. Say what it was out loud, even if there's no-one around to hear.
5. This is a bit of a mean one, so keep it to yourself! When you look at other videos, look for the mistakes or flaws in them. If you look hard enough they're always there because nobody is perfect. I've even spotted Felix slip a little. But even though that person made a mistake their video is still awesome, right? And yours is too. It's just that when you look at yourself you're looking at the flaws only. So remember that flaws don't stop you from being awesome.
With the trouble-shooting, it's understandable that you can't always figure out what you're doing wrong because it takes years of experience. It's probably better to ask someone more experienced.
Plus, it makes perfect sense from a motor learning perspective to go "That looks too slow, let's do it faster" and then just try to be faster without worrying about the specifics of how.
If it helps, my split grip is super slow too. I think the only thing I can do is get enough strength to do it on spinny.
