Yes, blueberry is a good strain to top, but remember not evey strain reacts well to topping, so make sure you read up on a strain before you go pinching it. And thats another thing, dont cut it with scissors, as this will stress it for no reason, you need to get your finger nails and pinch so that the stem heals quickly.

You'll get 2 main colas instead of one, and if you train the plants you can get up to 5 or more colas.