My Tailwhip Start.

 Most of those look like no foot can attempts more than tailwhip attempts... You've gotta just kick it with your strong foot (or back foot, depends what feels natural), then bring the other foot over the frame so it can spin. From there it's basically all arm movements until youre ready to catch it then you stick a foot out and catch it where it feels natural. Some like the seat, some like cranks, some like top tube. But some go straight to pedals.

 You need to get a significant more amount of air. No offense, but how are your jumping skills? Perhaps it is something you should work on first. Just getting use to being high in the air is an excellent start. Then try to learn tailwhips on a trick jump ( a step-up with a soft landing). Looks like there are some nice piles of dirt for you to use, just need some shaping or a wood kicker.

I'm currently trying to learn them as well, so no tips there except: Pump your arms hard to spin the bike, and try and get it under you as much as possible. I've got the full rotation, but I'm working on getting the bike underneath me.

 way faster, more air and kick HARD also once your feet are of the pedals push your wrists in a circular motion to roll the frame around you

 suck your legs up as high as you can

 good start