I think many auto body type air sanders are rated 6-7 cfm, which is at 25% duty cycle or 24 to 28 cfm actual, at 100 psi.
So unless you have a big tank, you better be thinking a 12-16 hp compressor. Don't be fooled by the tool ratings at 4-7 cfm which actually requires 4 times that.
Sand blasters of any size are outside my experience. Just beware the bogus industrial air rating system.
My compressor is no longer listed at Eatoncompressors, it was rated 3 hp (electric) , 3 cylinder, 2 stage. Without the huge tank for a buffer, my compressor would be hopelessly inadequate.
The 3 cylinder 18 cfm (free air) compressor they sell is not the same, and the 3 cylinder, 2 stage is larger capacity and too big for a 6/1, even at reduced rpm, I think.