I have taken videos before of me and Peanut, maybe he'll let me do another one so that I can post it. He's orange so obviously a lot easier to see the vein in the ear but along with the scruff, I shaved the edge of his ear so that I could clearly see what the heck I was doing when I first started. I think that helped a lot.
If you can find a lancet device that has a clear cap, it will make it easier to see where the pin is going into the ear. I am using the device from the Alpha Track even though I use a different meter. I do not like the devices with solid colored tops for this reason. I have my device set at level 1 and that works fine for me and for Peanut. I learned a little trick with the clear tops, if you run a black sharpie around the inside of the clear circle (where the lancet tip comes out) then you can really see where everything is when you put the device up to the cat's ear. If you have a black cat then just use a white paint pen. It makes a huge difference, trust me.
I had my cat's scruff shaved at the vets office so that I didn't traumatize him at home lol.
When I get ready to test him or inject him, we go to the little "vet counter" that I have set up for him on my dresser. I have a towel down for him to lay on and all of his things are already laid out. I have many different reasons for this. It's so that he knows what we are about to do, there is a routine and he knows exactly why I have brought him there. He usually just goes ahead and lays down for me but when he doesn't, I just gently pick up his front legs and pull them forward so that he lays down. Lately he's started rolling over on his side which makes it harder for me but at least I know that he's comfortable if he's willing to do that. I also have this little area set up because I won't forget anything which I've done many times when I was taking his things to him, wherever he was at the time. This way of doing it has just proven to be more convenient for both of us.
For a long time I did have a problem with him hiding under the bed when I went over to the treatment area to get everything out. He recognized the sound of the zipper on the bag, he knew the sound of the test strips moving around in the container, then he recognized the insulin bottle rolling around in the box. I had to avoid all of these things if I didn't want to spook him. He would still run under the bed and I would have to trick him into coming out by using the laser light which worked every single time lol. Now everything is out at all times, just sitting in one spot by the treatment area. I don't take the strips out anymore until I already have him laying down. I trained him to be okay with all of this by offering a treat after testing. Once I started doing that, I could ask "who wants a treat" and he would jump up onto the dresser.
I probably make it seem so easy because Peanut is really a dream child, I couldn't ask for a better cat but I do sympathize with people who are less fortunate. One other tip that I have for injection is to do some light massage all along the back and shoulder area beforehand. On Peanut, right before his injection, I pick up the scruff and let it fall back down about 5 times so that it becomes more relaxed and easier to grab. When he is laying down with his head down it pulls the skin tighter which makes it harder to grab any scruff so I get him to lift his head and loosen that skin before I begin.
One last thing, different ways of holding the syringe can affect your comfort, the cat's comfort, ability to inject, the needle bending and other things. Try different ways each time until you find the style that is right for you.
I think that perhaps now you're both learning how much better things are when there's insulin around you'll both start to feel better about the treatment. Cats are smart: Smiffy will join the dots and realise the injections are part of what's making her feel good again.