I found that the tape method the paint must be semi-dry and, having the chance to leave finger prints. The salt, well there is a chance that it will knock off during the spraying and handling. The liquid mask works well but you have to really pick at it to get it to lift off.
The one I found to be the better of all things is rubber cement. It is easier to control and apply.
For this feature 'm using a humvee kit. I applyed a base coat of nato green on to my model and let it dry for a day. Once dry take out the rubber cement and with a small brush apply where as needed. This stuff dry's fast, meaning that you don't have to wait to apply you final coat. Now i will spray my final coat of paint over the rubber cement and the entire humvee as well. Once the paint has dryed, start to rub of the cement with a finger, and when done it should look real, and no thick edges.
Rubber cement is cheap and can be bought at any office supply store.
I'm not saying that those metheds above don't work, I'm just saying that this is easier (for me atleast).
Give it a try on a scrap model.
I'm sure once you have, you'll use this methed often.