Semi dry is anything from 70% or higher isopropyl (what i used), or clean evaporating, checked msds denatured alcohol from the hardware store with ~25% distilled water added. Things you don't want in your denatured alcohol would be highly polar hydrocarbon solvents, tolulene, naptha, heptane, etc. Other alcohols are fine, like say 5% methanol, or ethyl acetate. But be aware of the toxicity of the denaturing agents, and use the proper safety precautions. Always make sure it cleanly evaps.
I think iso is your best bet, or if you can get a hold of everclear alcohol, that is one of the best solvents for cactus resin. Due to its low toxicity, and higher polarity than isopropyl. But iso works fine as well.
This will cause no swelling, or cactus snot. The alcohol breaks down the cell walls, and the water pulls the natural alkaloid salts. The mixture will not become thick, slimy, or snotty in any way, since there's not enough water, and the presence of the alcohol prevents the cell swelling that causes that mess.
And i'd look into making a herbal percolator vs. squeezing through a cloth, it will filter it much better with alot less loss of solvent and if you do it right, no sediment post filtering. Most of the time though, if you leave the vessel undisturbed for a day, all the powder will decant to the bottom, and you can carefully pour off most of the alcohol without any powder.
Alcohols are actually somewhere between polar/non-polar solvents, btw. They tend to be more polar than np, and can pull alkaloid salts without any water in some cases, but adding a bit of water ensures there's plenty of room for alkaloid salts to dissolve in the solution of alcohol/water.
So the mescaline/alkaloid natural salts are dissolving in both the water/alcohol, more so the water. But since too much water causes swelling and cactus snot, you use a binary solvent of ~70% alcohol, and 30% water. This allows the alcohol to prevent swelling, and breaks down the cell walls, and the water shoots the solubility of the natural alkaloid salts through the roof, vs dry (or pure, 100%, 200 proof) alcohol alone.
But, you will get a bit of fats/oils from the alcohol/water mix, due to how alcohols dissolve fats/oils (why they break down the cell walls) but are still a bit polar. So that's where the redissolving of your resin in slightly acidic water comes in, it leaves all that crap behind since pure slightly acidified distilled water is far to polar to dissolve the oils, IE they're insoluble, but the alkaloid salts are very soluble in water.
Like doing a distilled water wash on some hash oil made from ethanol, but for the opposite effect. To leave the fats/oils behind, and grab the highly water soluble alkaloid salts. The small amount of vinegar or hcl ensures no goodies get left behind.
