I too, am having this same problem. Probably not the best technique, compared to a professional smackrat or a doctor (or a doctor with his fingers in the cookie jar/the odd female patient), but I know how to do an IV, I know of, and follow sterile technique, including sterifiltration, other than if the case were to be a vial of something or other intended specifically already for IV/IM use were to be had.
I haven't buggered my veins either, I don't shoot often. Even when in a vein quite certainly (using very steady, yet not heavyhanded pressure when the vein is felt as 'feedback' through the tip of the needle, with some give etc, then suddenly, I know I am in the target vein, as I feel a rapid give in resistance, which is when registering is possible.
Possible, is one thing....easily doable is another entirely. I likely have low BP due to taking a fairly decent sized, although not vast or excessive dose of tizanidine daily (via RX), sometimes per os, sometimes, well...not parenterally and not orally, nor does it involve the nose

. I figure that is a bit of a nuisance....or on the other hand...question...would an ultrashort-acting vasodilator (low dose nitrite ester inhalation just prior to injecting perhaps...no...not injecting the nitrites, before anyone suggests that is a bad idea...christ, that wouldn't be pretty) make it easier to hit in practise?
I have experienced a vasoconstrictor (a couple of times when stimulants were given IV, a second dose of the drug was nearly impossible to register, went through several vials of sterile H2O, waaay too many 30g and 25g needles from my IV kit, before saying 'bollocks to it' and squirting the briefly registered, then lost solution out of the window and finding somewhere to properly dispose of the used, flame-sterilized, capped needles and rig used)
Not planning really on IVing the stimulant in question again, my DOC for IV use is MXE, which is MUCH easier to shoot. Doesn't have to be dissolved in EtOH and diluted down a great fucking well deal just to get a small amount of drug inside one either. Heh, no idea how, but somehow, I even manage to hit a lot of times while actually either coming up on an IM or SC, or just geing generally pretty squirrely by that time.
One major problem, and this includes completely non-squirrely, baseline, just-meets-postman packet status, is finding it really hard to draw back, even when IN the vein, or pretty damn well convinced of it, or to create a slight negative pressure prior to hitting the vein. Even using an easy vein to hit, such as a couple of large, shallowly located, very prominent ones located on the back of one hand, turning the lights in the room down to almost nothing so I can see better (autie, bright lights are a sin against nature and makers of cheaper brands of shades that won't double up when outside with a second pair

), using a 30g 1/2" needle, sod all comes through if I DO pull back a fair amount of the time.
And a couple of other problems-the plunger of the rig (3ml barrels) tries bending and flexing when depressed, any tips on how best to rest and stabilize the barrel itself from moving while administering the shot? trying to control a plunger that may as well be an ADHD snake with ehler's-danloss syndrome, whilst continuing to push IV in slowly is a real sodding pain and often results in slipping, and pulling back the needle until it is no longer resting within the vein, this goes for any injection site, not just hands. Back of the hand is just the easiest site for me, easier than any of the forearm veins or even the really large ones located near the brachial artery.
25g register easier, but I only have full length ones, and I really don't like anything other than 1/2" needles. I have a load of the things, and they will, if for some reason I can't use a 30g short, get used, and for a pre-prepared second or third shot, then they are getting pretty much dumped, when its both easier to register, and there is significant analgesia. Not going to use a large diameter needle either, for a shot in the hand, nothing wider than a 28g at the absolute worst, but I don't buy those anyway.
Anyone actually still get blood automatically flowing into the syringe when using such a narrow diameter needle?
Also, would it be reasonably safe to use a sterile, alcohol based gel lubricant to 'oil' the rubber seal on the end of the plunger of a syringe before use a little? Taking into account, while not meant for that use, it is a product intended for use in hospitals, so it is indeed sterile.
Last quick Q-how does one know, where venous valves are, and thus how to avoid hitting one, or penetrating from the side? I have never, to the best of my knowledge, actually done so, but I have no wish to either.
Gahh...I do hope my MXE and 5-MeO-DALT arrive tomorrow, been taking a break from MXE for a while, now its time to see how tolerance is responsive over time.