I haven't been able to record my attempts but as of the time of writing this I've been running an All-around Any% for the past 2 weeks with a PB of 20:19. Here's what I advise you do:

DISCLAIMER: I'm playing on the PAL version of Cool boarders 2 so timings may vary. I don't know if they do but it's something to keep in mind.

First off, pick Yaggi as your boarder and choose the 3rd AA board.

When you begin you'll do your first Big Air jump on Stadium Kicker. The combo I always do is Tail Grab to Melancholy while spinning in either direction. I do the same combo on Ice Fang too but I Fakie first.

When you are told to GO at the start of Stadium Kicker, you want to immediately Jump (I'll explain why in a moment) and the moment you land you want to prepare your spin by holding X. Just before you go down the slope, hold down left or right to charge your Spin and jump at the very end of the ramp for the most airtime. You'll then do Tail Grab (Down, Down, R2) and Melancholy (Down, R1, L2). If you land this you'll get between 780-982 points depending on how well you land. This normally shoots you up to first place.

Later on when you're on Ice Fang, instead of jumping you want to Fakie first, then hold down X to prepare jump. You want to start preparing your spin just under 1 second after you end your Fakie. Get to the of the Ramp, jump and do the same combo from earlier and you should get over 900 points.

Then you'll go on to the race. Since we're allowed to Skip Races here you want to skip the ones you take the longest time to complete. Pipeline Canyon and Freezing Point I think are the 2 longest tracks in the game so you can skip those. I usually also skip Snow Ruins since it's the hardest track for me to complete in the Championship. It is shorter than Bear in the Forest but it's such a tight circuit for me. Bear is also fairly tough but I can usually get through it without crashing and as a result I get through it quicker. It's up to you what 3rd track you skip.

Starting from White Resort, once you begin the race, immediately Jump forwards. I said to do this on Stadium Kicker too but the reason for doing this is that it gets you immediately up to top speed compared to not jumping. You can't pull this off on all Tracks however, here are all of the ones that don't work:

Bear in the Forest Freezing Point Winding River Snow Ruins

This is because you start the race on a downhill slope so you're already going quite fast, jumping here would just slow you down.

Finally, in order for this route to work you need to accumulate at least 48 points. Basically meaning you need to come first in all races except for one, that one race you can beat coming in 4th or higher.

Can this route be faster? Possibly, but it's a starting point at least. If I get the opportunity to complete a run I will show it in action.

Good luck!