Quicky and Sanding techniques explained (+ picture for P&S moc)

Still trying to make the most of good weather and the good light till late. Took the plunge last night and got the nail punch and hammer out .... yep I was gingerly wacking the roof. There where some high spots from panel beating it that I had to admit defeat and push them back down to get the roof level. Well worth it as this evenings sanding went much better and I have even started to go back over the rear pillars, yes this is the start of me going back over the car with a more experienced sanding technique, so the vast amount of hours sanding have no been completely waisted!
Yikes, this seems to be really worth while so deffinitaly going back over the whole care. Little sigh.

 So far the technique that is working well for me (there are plenty of different ways so do experiment) seems to be; For early stages of panel corection/dents and rust pits or panel repair, don't be shy with the filler as going back over it just drags it out longer and do try to keep it a bit smooth as this should make your mixed up filler go further especially as your going to sand a fair bit straight back off any way.
Sand paper 40g - 180g is for shaping, above that is primer sanding if using filler primer, if your doing normal primer us 250-600g before priming. When you get to 1000g DO NOT jump up more than 500g incriments, you can go up to 2000g before doing colour coat. Then if there is impefections in the paint use 2500 - 3500 ready for gloss coat and use a buffer to level/flattern the gloss coat.
Sanding pattern. Now this is super important but results are also affected by the size of your sanding block to the size of the panel as you can be sanding the main roof or a door pillar. Yep this is something you just work out! To give you some idea I am now using blocks at 140mm, 300mm & 450mm all about 40mm wide. The short block is used for super tight curves (corners of the roof as I have no roof gutter), the top corners of the rear window (a odd set of multiple angles and curves going on there) and the corners of the rear valance but I have only used 180g as 80 takes to much off to quickly. The 300 block is used with 80 & 180g really good on the middle of the roof (more opposing curves than you think) rear A pillars,  door pillars and rear vallance also some early shaping above the fronmt & rear window openings, The 450 block was really good for final shaping above all windows, the 4 sides of the roof, and the wings this was only used with no lower than 180g.
I have not bought or used flexible sanding blocks at all, as long as you sand in a Z pattern  as you can see bellow, the black lines going forward and the red on the return. I was doing this 4-6 times then would change direction to go back over the spot again, this is my way of speeding up as the profesional  worked more in a box shape doing the retun imediatley but I could not get a good rythm.

This does work on all curves and is amazing at showing the low spots, so you may have to get the filler back out to level off, but this is the time to go back over it as many times as you like with the quality of the paint job being 90% about prep. For the blended arches the block sanding does take a bit longer and I found slowly building up the shape and sanding multiple time easier to hold a even shape, but I was going over some one elses work not starting from scratch.

Whilst sanding I noticed 2 holes on the wheel arch next to the seat ?
I remember there only being a vinal covering going over it ...... so any ideas what they are for ? Seat belt anchor ? but why 2 holes ?
Verdict just in off a forum ... roll cage mounts, booo thats no help ! Rubbish will have to make them disapear then if I don't want road water inside.