Compressor ?

[rob love]

If theres one thing I wished I had done early, it would have been to buy a compressor that was way bigger than I needed. Instead, I now find myself holding 4 of them, each one getting progressively bigger.

When you talk about sandblasting are you talking about a small cabinet type blaster or are you talking about a portable blaster like you would do a hull with?
These are probobly the highest consumption products for air, closely followed by a paintgun. These things aside, you don't need too much a compressor to use airtools.
To use a common (non-HVLP) paintgun you will need at least a 5hp compressor. Even then you will be taxing it on a big job. My 10hp gas will keep up with the paintgun.
Sandblasting is another story.I use one of those Princess auto cabinet sandblasters($222 when they go onsale) for a lot of the work I do in my little workshop. I have modified the gun a bit to get a much better blast than what it would put out in stock form. To effectively run it I actually have to run two 3 cylinder compressors in tandem; one is a 3 hp electric and the other is the 10 hp gas. They will just about keep up with the demand of this single appliance. For outdoor blasting, I use a WW2 Ingersol Rand 105 cu ft air compressor trailer. This is getting a bit big for the in-the-city guys. I have tried to operate my sandblaster with a smaller ceramis oriface on the 10 hp gas compressor, but this is not overly effective.
I bought a nice 10hp electric at an auction last year which should meet all my indoor needs, but I have to replace the motor with a single phase and upgrade my shop to handle the 50 amps I will need to run it.

If you can farm out the sandblasting work, and keep the painting to a minimum, you should be able to get away with a 5 hp.
To figure out what you need look in the princess auto catalogue at the various airtools and their CFM useage. Then try and get a compressor that exceeds that useage by about 50% so that it does not have to run continuously. There is a big difference between using an impact gun for a couple of minutes at a time, and sparaying a quart of paint.