Hey Zebedee, I hope you're doing well. Those of us who really subscribe to the philosophy of Harm Reduction are typically very leary of dealing with substances of this nature. Acetylfentanyl is highly potent and a barely visible quantity could be enough to kill a healthy human being several times over. For this reason, we really can't adivse on a "safe" or totally vetted means of ingesting this stuff. Keeping this safe would involve you having an immense level of trust in your vendor, which I'm assuming you probably don't.
The best thing that you can do for yourself is to firstly, get a friend to stick with you the first time you try out this particular batch. If something goes wrong, you'll have someone functional enough to put you in the rescue position, provide CPR/Narcan and call an ambulance for you. Next, you should volumetrically dilute the solution, which it sounds like you were planning on doing anyway.
If it's a Hydrochloride Fentanyl, than you shouldn't have much issue with dissolving it into normal saline. I can't think of a great reason to use something like PG, seeing as how your product should already be quite soluble. Make sure you do an allergy test to start. Even if you're not allergic to Fentanyl, you could be allergic to something random than contaminated the product throughout the process of synthesis and packaging.
After the allergy test, conduct a very, very small insufflated dose. Wait 45-60 minutes and then redose if you feel you can handle it. You don't need to tread with this kind of extreme safety every time you dose, but you must practice extreme safety until you have at least a vague point of reference from which to go.
I don't know why people would spend money on Fentanyl. I know it's a matter of personal opinion, but Fentanyl is everything I dislike about Opioids without most of the stuff I like. It gets you very sedated and itchy and non-functional, but doesn't produce anywhere near the level of euphoria and bliss that real Opioids like Morphine or Heroin will.
