what would be a good primer to use after sanding car through clear coat

If everything is smooth and straight, I would recommend using a primer sealer. Any brand from a parts store should be fine. If you have imperfections, a high build filler primer can be used and quite helpful.

Do you know if Rustoleum primer sealer will do? How long can i have car exposed sealed off before deciding to paint?

That would work for you, but make sure it is going to work with the brand paint you plan to use for the final color. If the base of the primer and paint are incompadiable, the color will lift or give you a poor finish. Check with the parts store near you.

If you have the car down to bare metal, I wouldn't wait long at all to prime. The water in oxygen will cause it to rust if exposed within a few days. You should prime before leaving it for the day.

One other thought... If you are sanding to the bare metal, you should us a metal prep on the areas to be painted before priming.

My cell intention is not to goto bare metal. There are some areas that do need body work. Since car is not worth much I intend to paint with rustoleum oil based paint.

One quick question. If I did use rustoleum do I have to goto bare metal?

No. Just make sure to properly prep the vehicle before painting. NOTE: If you need to use body filler, then you will have to sand to bare metal at those places for the bondo to properly attach.

I meant how long after priming can i leave car to outside elements before painting?

The time it sits outside is really going to be based on if the metal starts rusting under the primer and bleeding through. Remember, primer really doesn't seal the metal. The paint does that.

So primer sealer will seal or not?

It should be okay for a while. Don't let it sit too too long.

It 's been 2 weeks since car has been primer sealed. I am going to paint it in another week or so. Car is dirty from driving to and from work. Can I clean car with soap and water?

Yes, it can be washed. Before painting, make sure to wipe it down with something that will remove oil and dirt. I always use the reducer which is used to thin the paint.