you can easilly remove the valve core w/ a tiny driver, or get a core driver from an auto store for like a buck. then put in a lot of air (w/ the wheel off the quad) w/ the core removed and turn the wheel around to get the water near the valve, this should get out every drop.
as for breaking the bead on an atv tire, yes it's 10x harder than doing a motorcycle tire. a motorcycle bead can be broken w/ a C clamp or a bead breaker clamp. an atv's front tire can be broken w/ a table vise, but it ain't easy. an atv rear tire might be able to be broken w/ a table vise, but the only way i've been able to do is by pinching the tire in a vise and cutting the steel right at the bead w/ a dremel.
also, if you're gonna try to pop the bead back on w/ lighter fluid, make sure you've got the core back in and your compressor on hand. as soon as you light it up it'll pop the bead but then the flame consumes a lot of the o2 in the tire, this will make the tire start to collapse on itself. you have to quickly fill the tire w/ air or remove the valve core.
i find it easier to just spray a ton of wd-40 on the bead prior to install and ratchet strap the tire and fill it up w/ way too much air, like 60-70 lbs.