From what I can tell from the Burroughs literature the anount of salt is quite important.

Here's what is says in my copy:

"The salt and water will not separate but will stay intact and quickly and thoroughly wash the entire tract in about one hour. Several eliminations will likely occur. The salt water has the same specific gravity as the blood, hence the kidneys cannot pick up the water and the blood cannot pick up the salt. This may be taken as often as needed for proper washing of the entire digestive system.

If the salt water does not work the first time, try adding a little more or a little less salt until the proper balance is found; or possible take extra water with or without salt. This often increases the activity. Remember, it can do no harm at any time. The colon needs a good washing, but do it the natural way—the salt water way."

So as long as you are eliminating most of the water in about an hour, you're doing it right and unfortunately there's no short cut. (As much as I wish there was one!)
Good luck