I've done it plenty of times, and it can be a very effective tool. It's definitely a "try it out and see" thing for me, I can't tell by looking what's going to be best. Starting with a delay equal to the backline seems reasonable, then try shorter or even longer if the drum fill is behind the drummer. Sometimes I end up delaying to the monitors or some reflection they are throwing off, or it turns out to be some odd distance halfway, or even none. I don't have SIA SMaart Live, so it's going to be guesswork for me for awhile longer!!
And don't obsess about it too much, because it's only going to be effective from where you are listening. It can't be perfectly dealyed everywhere.
As far as delay goes, if you are running biamped, definitely experiment with delaying your tops to your subs. It can make a world of difference.