It makes a huge mess,you can do it outside on a dry day if you have a plan of attack and use good materials.Do some more reasearch on metal,rust,coatings etc.POR 15 is about the best stuff I've used so far.
Any blasting, especially with a fine, lighweight blast media, will make a mess. Unless you have a farm or rural property where you can park the car in a field while blasting ...