The hose idea is a great idea. Ever since the first time I read Shine post about the fuel filter I've been filtering my spray bottle water. I use the kitchen sink's drinking water filter (screws onto the faucet). Works great. I'm sure any calcium or other minerals from well water is definitely not helping after I just payed good money for uniform fine wet/dry paper.
I use a National Detroit 600 (inline-as in a fast back and forth pattern) and I love it. Great sander. It's heavy but it saves lots of time. I think it's faster than my Dynabrade Orbital. And I can use 1/3 sheets so paper cost is negligible compared to having to use discs.
I start with a dry 600 Mirka Abranet (looks like window screen). I start at 600 since I ALWAYS level sand everything before buffing. I don't sand all the way level but I get close with the 600 and it's easy to see because it's dry. This stuff lasts FOREVER. I love the product. Probably the most valuable abrasive I've ever tried and amazing on the ND 600 sander. Then I switch to 800 to level it and work through the grits to 2500. It's a pretty good system. I didn't like dry sanding. Too dusty and the paper loaded. I didn't like orbitals. A minor/shallow inline scratch that I somehow missed in buffing can pass off as normal wear or a customer's scuff. A pigtail from an orbital that I somehow missed can come back to bite me in the butt later. To me it's not worth it. I still use orbitals for before the color coat (400 and courser) but the only thing that touches clear coat is the N/D inline and the buffer. I should say that the trizact system worked ok. It and Mirka Abralon (foam backed abrasive disc) got the job done and pretty well. I didn't have to spend much time buffing. But again, one or two tiny pigtails that you could see in the right light angle was enough to say bye bye to the Dynabrade for me.
Speaking of... and while I'm on the topic, I did a test a while back using foam backed abrasives. Quite a big difference even in the amount of gloss just with the two different sanding patterns/tools. This was the last time I used only an orbital sander before buffing and I probably won't ever return. The pictures of the test are of around 1000 or 1200 grit foam backed (can't remember off hand). I found foam backed abrasives to sand finer than regular paper without a backing... i.e. 1200 is closer to 1500 or 2000.