Re: Sandblast grit?
Use the lowest pressure that gets it done.
I always start low and work up to the agression level needed, especially on thinner metals like car bodies (which is mostly what I learned on.)
Lower pressure is also easier to control and less hard on equipment and consumables.
You start using big pressure and agressive media, you start using a lot more nozzles and air lines.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.