Correct order of sanding and body filling?

[88-SERIES200]

Hi i'm just about to start on the body work on my wagon and i want to know what is the correct order to do things in from start to being ready for paint.
I just want the right answers to clear up all the mixed advice i've been getting.
The car will need to be sanded back to bare metal in many spots such as the roof as there is alot of tiny pin sized rust dots over the old paint.
The car is being sprayed in 2pack with clear over colour and i have 1 k etch primer and 2 k high fill primer with 2 k thinners.
Some of the things i want cleared up are: When is it ok to body fill? i've been told to only do it on bare metal yet the tin says otherwise. whats the proper grit to sand guide coat? in what grit order do you sand from start to finish and when is it ok to wet rub?

[Reaper]

I'd stand first and fill later. Much easier to sand fresh air and no where near as dusty I find

Reaper