what do you mean "good"? pink sheets are complete baloney, mostly shell companies, otcbb can be traded at any brokerage I have ever heard of. Most otcbb's are baloney also except for very rare exceptions. Go to the dog track instead.
Can't trade 'em at IB afaik. There are enough shitty listed and Naz NM stocks, why throw money at chatroom and spam specials?
Used to be you could trade them at myTrack (www.mytrack.com). I think they were involved in something to make that marketplace more electronic, too. Don't know about shorting, though. That would seem to be a risk-management nightmare.