You're doing the right thing.Pick up some cheap thc test strips off fleabay.I pay about $1.25 each for mine.
I'm 6'2'' 280 lbs and if I'm smoking daily for a couple months it takes me about 3 weeks to get clean with no exercise. But everybody is different.
I'd do exactly as you're going to do.Pick up some quickfix and test strips isf a couple days before the test you're not testing clean go with quickfix. Be sure and practice with the quickfix.You can heat it up numerous times.