We used wet sandblasting for several years to restore the inside of aluminum bbq grills. It's the only practical way to get rid of the baked-on carbon and get back to a new aluminum finish. Dry sandblasting works on too small an area, is too slow, and carries a heavy risk of silicosis.
In order to wet sandblast, you need a powerful pressure washer. Ours has a 13 HP Honda engine, and produces 4,000 psi pressure at 4 gallons a minute. You rate and compare pressure washers by multiplying the prssure types the flow - ours therefore rates 16,000. For wet sandblasting, flow is important but pressure must be at least 3,500 psi.
We kept the sandblast sand in a garbage pail, and did not dry to recover it afterwards. In order to recover it, it has to be dried, which usually involves shoveling it into a spiral tube, turning the tube and transporting the wet sand over a heat source. Considering the low cost of sand, that was too much work for us. By the way, you must keep the sand supply far enough away from backsplash to keep it dry - it will not suck up into the hose if it is slightly damp.
We built a booth with a window to poke the sandblast wand through. The real problem was how to keep the wet sand from coming back through (as it hits a concave surface, it goes everywhere). We finally used those plastic strips used on warehouse doors to keep in A/C (and also on milk and ice cream trucks to keep them cold while unloading), but still, a lot of sand got back out, and the strips became opaque after a relatively short time, plus it's really hard to see what you're doing through wet plastic. You must wear mask and goggles (something like desert warfare tank goggles), but they also become covered with wet sand quickly.
The first time I tried it to see if it would work, it was in the back yard of the shop with a rental unit and no booth. It worked; it cleaned the inside of the grills just fine. But, I was completely covered from head to toe with wet sand. I could hardly walk...
We finally stopped the service because most of the newer upscale grills are stainless steel and the cast aluminum grills became too cheap to make it worth the cost of cleaning. The sandblasting was really never anything more than a marketing thing anyway; people were impressed that we got their grills that clean, but the carbon doesn't hurt anything, and it quickly reappears after a few grilling sessions.
Bottom line - it works, but you need a big pressure washer and a lot of effort to prevent a mess. Also, the nozzles are expensive - they last a while, but they are something like $100 to replace (this is for a serious, professional gun).
Almost forgot - hot water is not necessary, even for grease. The sand does the work; the water is only a carrier.