I'm not giving any kind of advice on IV'ing Fentanyl. As for smoking it, i would just dip out a small key bump size and do a couple til i was where i wanted to be, but i also wait 5-10 minutes before smoking another key bump. Usually 3-5 would get me where i wanted. My tolerance is moderate, I don't do opiates weekly. Mainly to keep my tolerance down. I do this with all drugs I constantly rotate my drugs of choice by the week and then next month go back around the selected drugs.