I have run intot he same issues that you are discussing. Here are a couple observations.
1. The water and scraping works great for popcorn celing texture removal.
2. It does not work on the walls.
If you want to retexture walls, you have 3 choices, and that is about it.
1. Rip down the drywall, and replace.
2. Apply compound over texture, and sand smooth.
3. Use lots of elbow grease, and and electric sander to remove existing texture down to drywall.
Sorry I don't have better news for you.
Good luck!