use your glute, man. I use 21g 1.5s into the glute. I can do them without even looking it's easy. Aspirating is simple; the plunger will be hard to pull back unless you're in a blood vessel. It's drawing a vacuum; you will see cavitation bubbles in the tube, or, since you were smart, those little ones you sucked up to the plunger gasket so you can force every drop out of the syringe will grow larger due to the lower pressure. Then, just progressively push the plunger, when you're done, pull it out progressively in a deliberate, continuous manner, and then put the cotton ball with the alcohol u were using to prep everything and press it right on the needle spot. Most of the time, you will see nary a trace of blood.
If you punch through some capillaries, you might see some come out, but pressure solves that and you'll have a bruise for a day or two. Otherwise, jeez...not a big deal even with 21s. I would use 23s if I was making this some kinda ED or EOD tip. For E7D, the ass is just too big to ever get messed up by a mere 250ml of something.
One of my suggestions is always stick slightly downward, so any bubbles are up at the plunger end, especially the ones you intentionally put in there to get the otherwise wasted juice through the pin base.