Find loose pinchable skin, pinch a little triangular tent with two fingers and use your other hand to make a little indent in the skin tent. Or, if you dog has lots of rolls just find one, hold it still and insert the needle. I use the smallest gauge and shortest needle available for canines to be sure the insertion is quick, easy and painless.
There’s no need to worry about air bubbles except that too many means not as much insulin is in the syringe as might be without them. Air bubbles are only dangerous if the shot is going into the blood stream but insulin shots go into fatty tissue. Just roll or tip the insulin bottle to mix the liquid and crystals at the bottom, never shake it, then insert the needle tip and draw until the top of the black plunger is at the number you are using as your dose.
Testing blood sugar doesn’t have to be stressful! Find a place you can easily access on your dog (I find ears too twitchy) so inside of the lip works for me and sugar. She is very used to be poked and prodded so she doesn’t mind. You can practice getting your dog comfortable by pretending to do the test and giving them a treat when they hold still and are relaxed. Now sugar knows she always gets a treat at the end and is very patient!