Have just tried the same method. It works. So, the steps are:
1. Enter the stage.
2. As soon, as you see "Go!", go to iGG and search (Number) 100.
3. When the search finishes, go back to the game and let zombies take some HP out.
4. Go to iGG and search (Fuzzy) "Smaller"
5. Repeat steps 3-4 untill you see less than 100 results.
6. Try to find the number the most proportional to your HP level in the game.
7. Hold it, then in the opened window name it whatever you like
8. Go to "Save" and change the value to 100.
9. Enable it.
10. Go to the game.
11. ...
PROFIT!
P.S. Although, it's pretty useles, as the stages are pretty short and doing these steps for every stage would take years.