I'd suggest getting rid of the problem altogether and stop smoking 
As for your actual question, I'm not sure, so hopefully someone else will have a better answer!
I like this idea. I've thought of trying to make pendants out of corks but they always turned out bulky and not working for me. I might try this when I get home and try using a clear varnish that I have that's used for clay see if that works. I would suggest either just pouring it down the whole to just coat the inside or it might be better to dip the whole thing in a clear coat sealant of some kind in order to avoid water retention like someone mentioned earlier...
Great idea! I've been getting into beading lately, so maybe a reamer will be even more helpful one day 
I'll take a look next time I'm around a craft store!
I like the idea too
any thick wire(coat hanger)that you can hold(pliers?) safely(it will get hot).
heat about an inch of the end over the stove(red hot) and slowly, gently move it through and around inside the hole, being careful not to push too hard as you may burn deeper than wanted.
id think a drill would tear up the cork more as cork has a very open grain, it may be safer to try burning the hole with a hot poker then a good wash out.
i have a little concern about the inside (loose cork) holding water in your dread. So i would def coat it. It may or may not be a problem but to be on the safe side, maybe not wear it when washing..or when hair is wet.
