I used to tap, slap, or "knock" on the area first but I've decided that that gives them too much time to worry about it and get all tore up. It seems to work best to just do it quick. First, wipe the area with alcohol and a cotton ball, then act like that's all you're gonna do for a second or two so they forget about it, then just smack the needle in there, fast and hard. Mine don't even act like they feel it that way.
If she still prances around even doing it that way, then do what you were talking about and smack her with just the needle and wait for her to settle before you attach the syringe.
What are you having to give her?
Baytril. She got two injections Thur and gets two more today and then he's coming back out mon. It's after it's in that she becomes a drama queen. I'm going to pop her with the syringe intact but if she jumps away I'm going to try just the needle the second time.