Hi Cheryl, some advice for you on the injection:
I am guessing it is sub q injection. I have a practice suggestion for you, and it is going to sounds really really stupid but it helps. Buy some peaches, or a similar soft fruit with 'skin'. Use one needle for practice. Fill it with water, and practice giving the peach injections. The texture of the needle entering a ripe peach feels like skin. You can't really tent the skin, but this technique is practiced often by Doctors to get the angle correct and stop the hands from shaking. Do it repeatedly, and be confident.
The nice part is you can still eat the peaches after!
When you give Josie the injection, be confident. Get someone to help you restrain her so she doesn't jump. When the needle hits pressure- don't stop, push even though it feels tough. It should only take a moment to 'pop' through the skin. If it feels like there is too much resistance, or seems like the needle is going too far without the 'pop', take it out and try a new place. It really doesn't hurt them much if at all when it is inserted. If the plunger feels too hard to push down on, you might be injecting into the skin. You just need to push the injection forward more.
The worst that can happen is you poke muscle (don't worry, you will know if this happens and it is unlikely). That might draw blood. Or nick a capillary, which may also draw blood. Or inject into the skin. In any of the outcomes, the rabbit will live and it will just take longer for the medicine to be absorbed into the body. I have done all three of the above- it is hard not to when you are giving 3 injections a day to several rabbits at a time! I felt bad but the rabbits didn't.
I know you can do it! And Josie may take awhile to show improvement. If there is one thing we can learn about rabbits, it is that they do everything by their own schedule.