I got a sears sand blaster for christmas and have used a synthetic media to clean up the underside of the car. Remember to plug up the frame rail holes. It makes rust repair so much easier. I have replaced the trunk pans,rear support and tail light paneland one floor pan.
This weekend I am taking out the drivetrain and will blast the engine bay. Including the cost of the blaster and two bags of media I have about 100 dollars invested. If you have the time and space it's worth doing yourself. Good Luck.

 

I wouldn't use a sand blaster..they make beads of tiny rubber like ***** that wouldn't even hurt trim pieces but does a nice clean job of removing the paint so you don't have to worry about the sand getting into seal and such...

 

how big of a tank for a car? 10 or more?

 

I've did a few sandblasting jobs. The cheapest way is to get one of those 20.00 siphon feed guns and a 5 gal plactic bucket. Go to your local sand and gravel pit and get the media mix that they use for drywall mortor. It cost me like 6 bucks for a 10 gallon pail. Just make sure you have good eye protection and a hood, otherwise shave your head bald as it gets everywhere.