Stop using soap and water.
Why do you say that?? soap and water is all we use.. its quick, works incredibly well, and is much cheaper than using rapid tac or equiv. Install etch dry is only a good choice if you're not very busy and have nothing better to do... Maybe someone can prove me wrong, but installing a 3' w x 5' h band of etchmark (your choice) - how long would it take you to install (clean the window, cut your material off the roll, install, and clean up) by yourself? Now I know there are many variables so lets settle that; interior install, install at 72" AFF, silicone on 2 sides with track top & bottom w/ minor silicone over edge of the flat polish glass.
Edit: I should also mention that it is a solid piece of etch w/ no cut outs or premask... but to make it interesting as well, what would your timing be like with x3 3" horizontal stripes spaced evenly in the height of the band and premasked?
Chaz