I guess you could use rubbing alcohol.... it will just take a lot longer to cure. In my mind.... I just can't see adding WATER to the mix. I get denatured alcohol in the paint dept. at Wally World, Home Depot, etc., and it costs about $3.95 per quart. It lasts such a long time... so I just buy it. I also use this to clean covering edges before adding repair patches etc. I even dump a little of this in my clean-up "brew". I did notice that rubbing alcohol comes in 2 different percentages. (about 70% or 90%). I usually like to keep the 90% handy when I am gluing with epoxy. I ALWAYS seem to get a gob of epoxy on my fingers, so I use this cheaper stuff just for cleaning my fingers that I don't contamimate coverings, clothes, etc.
Again...... it is NOT written in stone about not using rubbing alcohol...... but why not get the best and feel more confident with it?
As far as how thin to make the mixture.... I make mine as thin as I can, WITHOUT LOSING CONTROL and have it run all over. (the viscosity maybe something like pancake syrup???) The thinner it is, the longer the cure time. .... lownslo