Cars - Painting Prep/stripping..questions from novice

Hey...

Have some questions for the prep period between when the car is bare
metal and the first layer of paint. Im a little green on this and there
seems to be a lot of different brands/opinions etc.

I read a lot of "I like to use" or "A friend of my mine did it this
way"

Here are the questions:

After the car has been stripped to metal - What cleaner do you all use
to prevent that 'instant rust' issue -

Do you prime immediately? If so what brands are best?

When is an etching primer used?

After you put the primer on - you put the Guide coat to look for low
spots/help with the sanding etc - How much of this guide coat do you
put down and what brands are best?

I think that I have down the Body filler - no more that 1/8" - 1/16"
would be better - sand sand sand sand

Assuming all is done above - and body work is good - should you put
down another Primer/Sealer? If so what brand?

Thanks as always
Matt