primer over regular paint

Hi,

I've primed my Tamiya Toyota Supra and I've sprayed it with TS-17 (gloss aluminium paint).

However there were some bubbles in the paint and also the paint was too thick at some points.

I've sanded the thick paint off and I sanded the "bubbled" sections, and now the paintjob is, off course, butt-ugly.

I now want to repaint the car, but should I sand it entirely and then prime it and paint it, or could I just re-prime the sanded sections and then spray TS17 over it?

So basically my question is; is it possible to put primer over regular paint?

I don't see why you couldn't. Just make sure it won't react with the paint underneath it.

I would use some oven cleaner or westley's bleach white, or some castrol superclean to just strip the paint and start from scratch.

i primed over some revell enamel paint and it really tore up my paint job, had to sanf right back down and start over

As long as the primer is the same type as the paint you used, you should be alright.
As mentioned though, a safer alternative would be to strip the paint (see the Car Modeling FAQ on how to do this).

How much of the model did you sand?
If its only a very small area I'd make sure it is well smoothed and try a finish coat over the whole model.
If you have sanded a huge section and it will be noticeable, you really need to sand the whole model, prime and then repaint.

Well, it's a pretty large section.
Actually, the whole roof has been sanded...

strip it of, much safer and if you prime and paint again you will have a lot of coats on it, maybe to much.

The deciding factor should be how much paint will you have to build up to make the color uniform.
TS-17 will require a few coats to make it look uniform and may end up obscuring some details or just looking thick.
If you were shooting a more opaque color I'd say just paint right over what you have done.
Otherwise it would be best to strip it. Try 90+% rubbing alcohol, oven cleaner won't remove TS paint.
If you still want to prime and paint, used the Tamiya Fine Primer and you can blend the Aluminum color over it.