Hi Cameron:
All the advice you received so far is good stuff. I do a sand blasting day every summer at the S&P Museum (
www.calnan.com/swords) and, as we have 40 acres, we call a mobile unit in. People involved in the museum who want something blasted are contacted and the deal is you pay for the sand you use plus a share of the time used. Comes to $1000 to 1500 for a full day (7 hours+1) of blasting (we end up paying the travel time as well and he is 1/2 an hour from us). I usually manage to get the museum stuff done for the cost of the sand by offering the extra time to all the other guys who need big things like frames and rims done. Two years ago we did a complete Alligator, a complete M135, two truck frames, several axles, a dozen rims and a whole pile of sheet metal and the cost to the museum at the end of the day was $550 as the other guys picked up most of the $1500 tab.
We prep everything in the days before he arrives so that everything is stripped to the appropriate degree, masking is in place where needed (heavy cardboard and duct tape will withstand the blast) and the team is ready to move stuff for the blaster. By us doing the prep, he focusses on blasting and filling the hopper (and sucking down a lot of cold lemonade... it is hot in one of those suits!). He appreciates the help and the guys get to see the results as he is going along so they can ask for more work where needed.
The sand mostly ends up on the growing beach beside one of our frog ponds and the stuff is hauled away from the blasting site and primed right away by the crew with the paint spray guns about 100 metres away!
My point is: let the pro do the dirty work for you... as someone else mentioned he can strip a tank in an hour or so and we would take a week just doing the turret!
Buy your volunteers the white throwaway paintsuits (tape up the ankles and wrists), good sturdy work gloves, safety googles and paint masks so that any dust they are exposed to is negligible and make sure you have several coolers filled with ice cold lemonade (leave the beer for after the dangerous work is done)!
Good luck! Mike