Shoot them together in the same syringe.
The only issue that arises is if you want to shoot the slin + HGH immediately post workout (like in bathroom at gym.) this is because HGH is quite fragile, and is harder to carry it to the gym with you, while exposed to "room-temperature" for 1+ hours...
I don't really trust taking reconstituted HGH preloaded to the gym. Unless you've got some sort of mini-fridge set up in your car
You will still be okay with injecting slin immediately post workout and HGH a few minutes later when you get home/back to your fridge or whatever.. so whatever works.
[edit] Apology, I didn't answer the second part of your question.....
Make sure to get your blood glucose levels checked every 2-3 of months if possible, as this will be a key indicator of persisting insulin issues/dependency.