I usually use gloss WOP - cured WOP is impervious to alcohol. I typically apply 4-5 coats, waiting a couple of hours between applications. I have a couple of 'finishing mandrels' - maple blocks that have been drilled and tapped to screw onto the spindle of my lathe, and with a 3/8x16 bolt embedded in the end to hold stoppers. There is usually a little runout on these, so I don't use them for turning, but they are fine for applying finish. Having a few of these makes it possible to not 'mortgage' the lathe to partially-finished stoppers while the WOP is curing between applications.
By the way, I always apply a coat of finish to the underside of stoppers. Stoppers generally don't require serious washing, but it's common to rinse them off between uses. Applying a coat of WOP to the underside seals the wood so that water can't penetrate the wood and cause mold.
Recently, I gave myself a 'self-assignment' to do a captive ring on a stopper. Captive rings have to be finished in two steps - the outer portion is finished after the surface is rounded over but before the ring is cut free. Then, the underside is finished after the turning has been completed. Since I didn't want to extend the project in order to apply multiple applications of WOP, I opted to use Tung Oil instead, using the 'fat over lean' technique - the first application was a 1:1 mixture of pure Tung Oil and turpentine. After burnishing at high speed, I applied a second application of pure Tung Oil straight from the bottle. Burnishing at high speed caused it to cure enough to be able to immediately cut the ring free and then complete the stopper without further delay. The result is actually quite nice - a soft matte finish.
I really enjoy making stoppers, and they are great gifts to accompany a bottle of wine when invited to friends home for parties. The down side is that they encourage a really bad habit - leftover wine.