edit: K I'm back
If yers is the same set up as the one I used the most, this is np - if yers is a lil different... well the theory and problems are the same anyway lol
The valve closest to the tank, directly underneath and is connected to the tank on one side and the heavy sand hose on the other can be used to help regulate the sand flow to an extent. Using it in this way will increase wear on the valve ball as the sand hits it on it's way by and you'll be more prone to tank clogs. Tank clogs are easy to deal with by just tapping it rhythmically with the side of your shoe as you work, but this only helps prevent clogging - you'll need to kick/thump it a bit if it does stuff up. I've found that picking up the tank about half a foot and dropping it works pretty well too lol
It's tempting to use the ball valve nearest the handle (the one you hold while working) to regulate as you work, unfortunately not only does this increase the likelihood of the more difficult to deal with hose clogs, it's moderately dangerous as the wear rate on that valve is exponentially more due to the increased velocity of the sand/air mix. The "ball" part of the valve will wear
very quickly and the deflected sand will etch through the valve's housing and result in a blow-out. It's somewhat exciting, makes a fairly loud noise, and can leave you with a stinging welt not unlike road-rash. As tempting as it may be - don't use that valve to regulate and make sure to turn it to the completely on/completely off positions as quickly as possible to reduce wear.
The easiest way to deal with hose clogs is to simply shut down the valve closest to the tank, remove the valve closest to the handle and reopen the one closest to the tank - blowing out the hose and the pound or so of sand stuck in it, then shutting down again before you loose all of your sand.
Fortunately these valves are comparatively inexpensive, I think they run about five bucks or so. Periodic disassembly and inspection would be a good idea, "pipe tape" and whatnot is unnecessary, though they can last quite a while - they are disposable as nothing can withstand 'Black Beauty' for long lol.
It's actually much the same as finding the right fuel/air mix for our bikes. While with the sandblaster it isn't as needful - if you can find just the right combo of pressure/sand grit you'll find it far easier to work steadily and with fewer clogs. I suppose technically these valves weren't intended for this - yet after resurfacing any number of aluminum boats with that particular pressurized blaster, I've found these lil tweaks can really help.
A lil more rambling on;
Tip clogs: I keep a length of safety wire loosely clipped to the handle while I work, when the tip clogs shut off the valve under the tank and probe the tip with the wire. You can use the valve closest to the handle but I've found that one usually leaks just enough to maintain pressure behind the clog - preventing you from picking it clear.
Masking: Obviously masking tape alone won't withstand sandblasting at all. There are specialty products made for shielding parts and to make nice, crisp lines - but they're expensive, not easy to find in small hobbyist quantities, and quite hard to find (I'll look if yer interested). While masking for waterlines on those boats, I've found a layer of blue masking tape (known as three-day tape) with a layer of tin tape over it and another layer of blue masking over that works well enough.
It wont last long, but it does work well. The top layer of blue is your "warning" layer, it shows how much you've hit that area. The layer of tin tape is all that stops the sand, but the layer of blue under it all cushions the impact a bit, allows the tin tape to take a little more abuse and gives you a last second warning before you cut through. It's a cheap and effective method of masking crisp lines, it does take a bit of practice - I tend to do all my edging first with an inch or so of border - then I go on to finish the large areas.
I know it's obvious, but remember to not get this "sand" all over the place. We had a newbie blasting a boat here at the marina and he managed to get sand in a couple of other boats. Every bilge had to be cleaned spotless and every bilge pump replaced as a result. It's sure to destroy bike bearings in short order and it manages to get
everywhere despite how hard you try to prevent it - a cabinet or closet is defo the best way to go
wow - that ended up to be quite the rant lol Sandblasting is awesome - but I've seen so many give up cause it's not as easy as it looks. The tool itself is finicky but with practice it's fine - the most common problem is damp sand. Even fresh from the store it tends to be just moist enough to cause problems - you need it dry as a bone to work easy.
