There is a technique called a "z track" injection that works for areas that have more fat, like glutes. My delts never really have much fat on them and it would be hard to use this technique with only one hand. Basically, after you clean the site, you pull the skin over and hold it there, as you put the needle in. After you pull pull out, the dermal layer covers the hole back up.

For your situation, the best you can probably do, is have an alcohol wipe handy, and cover the hole as soon as you pull the pin out. Another option may be to use a smaller sized needle. Obviously, the larger the hole, the larger the hole is going to be. Geneza gear is very thin, made from an MCT oil and travels through a 25g pin just fine. Finally, you may be injecting too much into one site. For delts, I wouldn't go past 2cc, and I have pretty decent delts. Even at 2cc, I feel that the swelling and oil does distort the shape of my muscle for a short time. 

Really, at the end of the day, I wouldn't worry too much about this. The few mg's you lose isn't going to make a difference in your gains.