iso swab, insert & register, push down slowly on the plunger as you count out loud "one-two-three-four-five." then withdraw the needle and apply hygienic pressure to the injection site. This should hypothetically yield a flow rate of 2mL/second, which is ALREADY A LOT so you should consider going even slower. You are using an obscene amount of water for the opioid you're using in question...
Seriously.... I mean I can understand down508s advice being acceptable if the OP were SNORTING, but for injection? You don't ever inject something that's been exposed to the elements overnight... No.... Just.... so no...