Is there anyone online who has got this Doug Tewel thing working well? I am playing with it at the moment but not too much success yet.
Nope. I make it a point to avoid the "10 FREE LESSONS!" guys ever since I wasted my time on PPGS. I'd rather bomb the ball and take my chances than dink it around the course with dead straight 150 yard drives.
I would take a look here if I were you.
Pretty hard to beat the quality (and value) of the instruction these guys offer. You can do it all online and they don't teach one particular swing, they work on improving what you already have. Plus they run this site so you have quite a bit of "free" access to them. A lot of us members here are learning from them so the support group is pretty huge and you can get a lot of help from fellow members who may be working on the same pieces as you or have worked on them previously.
The website is here: http://evolvr.thegolfevolution.com
Do a little research on setting up you camera angles and filming your swing first so that your giving them decent material to work with. 120fps or more is ideal but you can do it with regular speed film as well. Here's some tips on filming: http://evolvr.thegolfevolution.com/library/filming_your_swing_reference#notes
I'm also tagging Erik @iacas to this thread as he is the Director of Instruction and may have some comments.