You are not always going to be able to grab an offensive rebound with both hands. Sometimes you are going to need to tip the ball out to yourself so that you can grab it. If are able to tip the basketball out to yourself then this is the perfect time to attack the basket, but you need to do it quickly.
The reason that it is a great time to attack is because your defender is most likely out of defensive position because they have just been jumping with you trying to get the rebound themselves. If you can grab the ball and then quick attack before they get set, you will most likely either get a finish or a blocking foul on them. Here is a great basketball rebounding drill that you can use to practice tipping the basketball to yourself and then using the quick attack finish.