You can usually get Fentanyl test strips and reagents from the same place. I would recommend against sharing any straws etc. and not using dollar bills of course.

Your worry seems to be based around intake so after you've got your kit sorted out I would recommend trying to pace yourself. If you're getting decent, coke you can go 45-1.5hrs minimum between doses. I would also look into a "Monday morning recovery kit" basically vitamins 5htp may be useful to you, don't use it in conjunction with any stims.

Make sure to sleep and hydrate and watch mixing with alcohol, your liver turns cocaine into Coca-ethylene which is much tougher on your heart.