I'd shoot them together, saves pins, less sadistic.
Just make sure that you follow sterile procedures for both bottles and yer good to go!
I know that last part is kind of a duh, but the first cycle I ran where I was mixing multiple drugs in the same syringe, I mopped the top of the test vial and drew it and without thinking I just pulled the ultragan from the second without a swab and proceeded to stick it in my glute.
WHen I realized what I'd done I sweated the whole week until I was sure I hadn't shot myself with some funk. Ultimately I was ok, but the nerves were a bit the worse for wear.
