Hey, I have kind of the same problem, exvcept my hot spot was my left arm inner elbow but once I OD´d on h and k (I od´d on the H but the IV K didn´t help as I instantly passed out with the needle in and I fell over my arm and when my family found me and called the paramedics they gave me naloxone but when they removed the needle it was a bloody mess and blood started coming out so I had to get it even more open to see what was causing the bleeding and then after they gave me antibiotics whilst I was on w-d´s they stiched me with no painkillers, finding another sweet spot was hard, and I didn´t do much rotation at first, and the veins on my arm are deep and I should use a tourniquet, but I was a junkie and would rather poke myself 40 times and shave my legs to be able to see the veins there, i used to use .29 or .31 Terumos when I started mainlining and had my spot, fast discrete and efficient.
I quit Heroin, and daily IV use, though I´m getting good quality blow lately and i´m rxd morphine and can get midazolam vials, so I indulge a couple times a week, now my hot spot is a fat visible vein on my left hand, I actually have 3 big ones on my hand, but registering and keeping the angle with smaller gauges is way more difficult and even a waste now I registered and when i´m about to pull the plunger since they are so tiny I miss or feel i got out, so now my syringe of choice is a .27 Tuberculine 1ml Terumo, or if they don´t carry terumos I go with .25 BD also tuberculine, I backload since I generally don´t have a micron with me when I have loads of drugs, only when I have weed and pills...anyway I leave 5-10 units with air at the top before shooting with the bigger gauges and as soon as it registered the crimson cloud comes instantly and way faster than wioth smaller gauges, yeah I get marks in my hand, but now it´s winter and I have sore hands anyway and wear gloves, and generally I shoot in the weekend or when the big cheeses at work are away.
Fuck, once I was sleepless at work and we had LOADS of .21 Butterflies at the Phlebotomogist room with 10ml syringes to draw blood, dunno why they used such a big gauge, I talked with the clinical samples analizer and asked but I was on phenobarbital and remember shit about what she told me, i hope I didn´t came off as a junky, though the lab owner knows my whole rap sheet and I spend every damn day there and she comes once a week.
Anyway I had extracted methylphenidate crystals and loaded about 40mgs (took a plastic spoon from the coffee machine) and used about 80units with this big ass syringe, and I left more than usual air i leave at the top, it was painful as fuck, but it was so much more comfortable to put the syring on the table and only having to worry about the needle, well at the second I hit my left hand usual vein the syringe instantly was filled with cold dark blood I pressed the plunger easily but man did it hurt!! and how I bleed afterwards, luckily I dissinfected made a compress and put me a big band aid and went stright to my laptop, 2 dyas later I still had the mark, but I never registered that easily before, I don´t reccomend iVing with .21´s, but a .25*.27 could be a good start, and if you can get higher gauge butterflies i deffinitely recomend them for rolling veins and angle problems.
Generally I feel no pain, I´m right handed but I´ve abused my right arm badly after or whilst taking a shower with a tourniquet and could always register easier with .25´s, it never hurted, only once I shot coke, but I think it was a strange reaction to the cut and using a vein I don´t generally use cause I had hit my hand the day before, now i just stick to my hand and always dissinfect my hands, try to have the cleanest gear, ampoules if possible or filter very well if doing stupid stuff like shooting pills, anyway after my experience with the right arm I stick to my hands, sometimes I hit my right hand now though it´s harder to keep steady since as I said I´m right handed...
Hope this advice was useful, if you iv daily don´t use .25s, and neither your hands, but for me it´s the way it works.
But .27s (I always buy by the handful since I can ask behind the counter and we don´t have stupid laws regarding needles) so I mostly reuse 3-4times if I´m shooting coke and I´m too paranoid to move, and I always reccomend a new spike for each shot, they cost cents, order a box off the internet if you can´t buy bthem at pharmacies at your state.
With good technique and a medical ¨spaghetti¨tourniquet you always wash with alcohol or at least detergent before use, a steamy shower before or during the shot and leaving about 10units of air at the top you´ll have it easier registering, about the pain you feel though I dunno, try with a bigger gauge and if it´s worse maybe you should lay off for a while and use another ROA, do some push ups every night and your sweet spot will be as easy to hit like iot was before.
Me, I don´t like doing push ups...