How long should I let the base-coat dry berore rubbing it down.  How long after clearcoat before rubbing?

basecoat can usually be wetsanded around 2 hours after application provided it wasnt too hot when you put it on, the temp out can affect drying time.  Clearcoat you should wait at least 24 to 48 hours before wetsanding or applying compound.  however if there is a problem with the clear and you want to redo it, it can be wet sanded after 2 hours also.

I meant with rubbing compound.

you dont need to rub down the basecoat with compound.  you will need to wetsand it, and as for using rubbing compound on clear coat i would wait 3 days. but you could do it after 24 hours if you want

You can use rubbning compound on the basecoat if you like to smooth it, but normally you don't. Depends if you are spraying or touching up.