That doesn't seem correct. Adding that much extra air should make the liquid push into the syringe on its own. You really only need about 10% more air than the amount you're drawing. The usual issue is actually a vacuum from not adding enough air to replace the fluid. You can fix either problem by taking the plunger out after the needle is in the vial, or by pulling some extra air into the syringe along with your diluent before mixing. With either approach you end up injecting almost exactly the same volume of air as the fluid you remove. Very fine needles like 31G or 32G can also slow things down.
It's really tough for me to reduce the pressure inside the vial during draws. Even though I'm putting in 2-3 times more air than the dose amount in mg, the pressure stays way too high, making withdrawal hard, and when I remove the needle, liquid shoots out from the stopper and needle. Any suggestions? Should I add even more air?