Retest every day, though accuracy of chlorine testing will not be good until you get the taylor kit. Many pool problems are the result of not testing everyday, and inaccurate testing using strips or the pool store. I am sorry, I just noticed the size of your pool was 25K (thought I read 20K earlier), so would add 3 bottles of bleach.

I am not familiar with gunite pools, so maybe someone else can chime in with what kind of brush to use.

Just to clarify, you will need to use a chlorine source in the future that has calcium in it, you just don't need the stabilizer in the pucks right now. Again, someone familiar with gunite pools can add to this.