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Welcome Rodger
I will try to help, but there are some way more experienced that can answer some of your questions.

1) surfactant is the last thing you want to add, as it will start to breakdown the SH, and depending on the surfactant it could be a huge bubbly mess.
2) no , not really depending on what you use , it may need an occasional stir on the job.
3) this is something you will get with experience and no one I know sends anything out for testing, There is a thread to help with clarifying how hot your SH is.
4) None that I have heard of, most of your mix & Sh should not be contaminated with larger particles, but microscopic ones are nothing to worry about. It may also depends on your set up, but generally I would not concern if you keep your mix clean.

If you use the search button on the open side you will find a great deal more info from many,
Search term - filter.. Surfactant, SH testing etc.

http://roof-cleaning-institute.activeboard.com/p/results/

Others will chime in soon, patience is King here as most guys are out working most days

Take Care,

Kim R