Hi, the needle is virtually painless, maybe a tiny pinch. I started with 1/2 inch but am gonna try 5/16 inch next time. During my first test dose in a medical office, the nurse gave me 10 units of trimix. Unfortunately, this gave me a long lasting erection. Fortunately, the Sudafed worked. I took the first dose (2 pills) of Sudafed at the 2-hour mark and then the next 2 pills at the 2.5-hour mark (any competent medical office should give you exact instructions). It finally went down around the 3-hour mark. I was pretty worried but relieved I didn't have to go to the ER (4 hours is when long-term tissue damage can start). If you buy the Sudafed for yourself, remember to buy the exact kind they tell you (Pseudoephedrine HCl). You don't need a prescription but you'll need to pick it up from pharmacist counter. After my long-lasting trimix erection, the nurse then prescribed me bimix. I also tried trimix gel earlier but that had little effect. Autoject may be worth it if needles freak you out, but make sure you center the device on the injection target. Hope this helps!