I've never done it through combat, you can trigger an overdose by shaking your hips via the masturbation menu four times in a row. If you only take one, it's a 20% chance on the fourth (and further) shake, but generally you should just use five doses of Thicc & Shake since five doses both guarantees the overdose happening on the fourth shake and getting a perk from said overdose. I'm not sure, but it may have a minimum lust requirement, in which case I'd recommend just drinking from Ellie's tits, since one of the vending machines you can get T&C from is in the BBQ place directly across the hall from Ellie's gift shop, and drinking from her temporarily raises minimum lust.