As far as you're concerned, it's just buying/selling in reverse. There is no waiting period.
When you short-sell, you're technically <i>borrowing</i> the shares first, and then selling them on the market. When you cover your short, you're buying the shares back to give back to the borrower.
In actuality, your broker takes the responsibility of borrowing the shares for you, and it's all instantaneous; as far as you're concerned, it's no different than a normal long position, just that it's in reverse. Your broker borrows the shares, or you 'borrow' them from the broker's own stash; when you cover, you're buying the shares back for your broker. There's no waiting period, and no extra work to be done by you.
All you have to worry about is whether or not the shares are shortable, according to your broker; that's your broker's business though, and obviously they won't let you short-sell shares that aren't on their shortable list. Shares may be considered un-shortable, for example, if your broker doesn't have them available and doesn't feel like borrowing them.
The up-tick rule (which used to be in effect, and may be again) simply means that you can't short-sell a stock unless its last movement was an up-tick. Which means that you have to wait for the next up-tick for your short to actually be executed. Which means simply that your trade may (or may not) take a few extra seconds to execute, if and/or when they reinstate the up-tick rule.
Is short-selling a viable strategy for a day-trader? Of course. Almost every day trader in the world does both long and short positions, routinely, depending on market conditions. I haven't ever specifically met a day trader who only trades long positions. I'm sure they do exist, but the overwhelming majority go both ways when it comes to that.
I'm sure you could use services such as locatestocks.com if you wanted to, in addition to IB's services, but I don't see why it would be necessary.
Did that answer all of your questions about shorting?