You can maximize damage as brand through two ways, first by consistently landing skillshots so that the enemy would always be Ablazed. The most ideal pacing on Brand’s abilities is once every two seconds.
The second way is to burst down enemies and quickly apply the Detonation of the Blaze passive by quickly using all the basic abilities in quick succession. You have to have a clean hit for Brand’s 1st ability, Sear and the ideal combo progression is 3rd > 1st > 2nd.