Mr. Surfacer 500/1000 Questions

Men,

Went to one of my good hooby stores here in New Jersey (Jersey Shore Hobbies) yesterday to get Armor Model Tracks for my T-55 project, and also picked up the above mentioned products, which I have been wanting to try for the some time.
I have seen it used by our fellow builders here at WW2MM, and have the following questions:

1. Recommended appplications?
2. Brsuh clean up? what do you recommend?
3. Recommended surfacae area coverage?
4. Has anyone used the 500 that comes in a spray can? this would seem useful for large "cast" areas.
5. When do you cross the line from 500 to 1000..for example which would you recommend for a KV-1 turret casting surface..and what are the different recommended uses for 500 vs 1000?

Currently I am considering using it to fill and cover the injector pin marks I was unable to sand away on the Armor Model Tarcks that I bought..any recommmendations here? Also thinking of using it to tie in brass infantry rails on T-55 that I am building...where the weld would be for the railing being attached to the turret side.

Thanks

Bob Stodnick