I have had it take an hour. Usually just a few minutes (or seconds). Through the API I just make the trade, then I have to watch it until I get filled or I cancel the trade (and make sure the trade really was canceled). They have been very good, in my experience, unlike most retail brokers with very limited shares available for shorting. I have no idea where they go to find shortable shares that they don't have locally.
GURU, Watch this video titled: IB Short Video: Pre-Borrow US Stocks for Shorting https://www.interactivebrokers.com.hk/en/general/education/videos/pre-borrow-us-stocks-shorting.php and a screen shot you requested.. but watch the video for details on how to enroll along with costs and requirements (ie. must be portfolio margin account) For Hong Kong SEHK: if any of you are serious about pre-borrowing, send me a PM and I'll introduce you to the appropriate team.