I'd have to agree with ODT for once, Stochs on multiple time frames can be very useful but you do still have to apply discretion and not trade off the indicator alone. Overbought/oversold areas are less usefull IMO. And of course your trade management following entry is absolutely key. Many things used in PA are lagging as well BTW - trend lines and price charts themselves are lagging databases for example.
If you consider looking at the daily with 5,3,3 and around 20,12,12/25,15,15Stochs what do you see? The higher Stoch shows if the market is trending on the weekly, and the lower stoch shows pullbacks on the daily. Adding a couple of moving averages (don't look for a cross it just saves time drawing trend lines in) helps in taking the 'with trend' moves rather than the countertrend ones. So this is a trade on the weekly with timing on the daily.
The other way of using them is from the bottom up rather than the top down which is how price is actually moving so you're lookng at the stoch to do something for example on the 5 min, then 15 min then the hourly - so here we're trading on the hourly and hopefully have the smaller timeframes building up a head of steam to push the hourly in the same direction, this tends to be more of a countertrend strategy which by it's nature can be risker but gets you in at the start of a move.
All of this of course can be done purely with PA so yes, the indicators aren't really needed at all, but where they are quite useful in showing what's going on from different time perspectives all on the one chart.
I wouldn't recommend using the Stochs as an indication of when to exit at all, just as a rough guider to show the area where to try to pin the tail on the donkey, much the same as drawing in trend lines etc.
