I have done shanka prakshalana several times and I have learned that different people do it in different ways. The one key thing is the ratio of salt to water, the idea is to make this solution the same ratio as it is in the body, if the ratio is too high or too low, your body will absorb a large amount of the sodium instead of just letting the mixture pass through. Since all people have different amounts of sodium in their bodies, the only proper way to make the solution is by tasting the sodium levels in your own body and matching this to the taste of the solution that you make. To do this, put your little finger up your nose high enough so you reach the liquid part, then you taste this, then just match the same salty taste in the solution you are making. For this to work properly, you will need to drink the solution fairly quickly (but not too quickly of course) and the amount you will need to use will vary from person to person, but you keep going until you have clear bowel movements. It will be easier to achieve good results on a full moon or just before the full moon, best to do in morning time.