man what the fuck, what the actual fuck
smoke, drink, smoke, drink, smoke, drink. You combine the two and keep them combined. If you're calling it lean I'm assuming you'll be sippin' on a mixed drink, so pour a 4 while you smoke, take a few sips, keep smokin', sip, sip sip, find something to do while you sip, smoke again, sip and smoke, sip sip sip, pass the fuck out.
If you're dosing it as cough syrup then hit yourself with 15-30mL initially before smoking, and throw yourself another 5-10mL whenever you feel like you need a pick me up (or bring-me-down, in this case.) Once you hit two ounces, though, slow down. Keep in mind that a single dose is typically 5mL. As a first timer you don't really want to press your luck with what your body's capable of tolerating. If you've got experience and a bit of tolerance, use more discretion with dosage amounts but still space them out whilst smoking. Slow down around 4oz, and fucking STOP once you hit 6oz in 24hrs.