Flash your mate to into his Car peak and immediately after burn the Half Wall as shown, so a flashed T cannot retreat neither can his team support him.

This is a better spot to throw retake utility from than standing on the Coffins - as most people do - that not only exposes yourself to Banana but also might make them hear the grenade pins being pulled. Always go with the first two of the list that are shown here, then situationally you can follow up with the Halfwall Smoke to secure Car control or the Deep Banana flash to help your mate fully clear Banana.

1. Flashbang Car
2. Molotov Halfwall
   3.1 Smoke Halfwall
   3.2 Flashbang Deep Banana

Thrown by SZPERO.