I too have a problem with choking down a quart of salt water. The celtic salt is mild, but after a couple of days of that, my stomach just won't keep it down - it goes down and immediately comes right back up and the HLT is sickening too, so I didn't take any for 3 days and wow did I feel crappy, so I did the HLT (herbal laxative tea last night) and let it sit until it was room temperature and then gulped it down and followed it with water and that was fine and this morning I tried your trick - I put the salt in a glass and some boiling water to dissolve it, then some more water and gulped down some room temperature water, then swallowed the SWF (Salt-Water-Flush) down fast and since it was only about 1/4c it went down real fast and more importantly, stayed down and then I immediately followed it with the rest of the water and instead of waiting an hour to 1.5 hours for it to work as has been the norm of late, it started working within 15 minutes and man, did it work!! I feel 10 pounds lighter and I see nothing in the Master-Cleanse book itself where this variation can't be done - it works for me and it's the only way that it'll stay down and you know something else? I have no salt taste that I was getting before, which lasted all day.
I think I couldn't take it that well before because I actually cut salt out of my diet about 3 years ago and am one of those people who would get fries from McDonalds WITHOUT salt, because it made me sick to my stomach.
I know some of the hardcore MC'ers won't like what I've said, but you know something - everyBODY is different and this works for me (so far) just super!!