Brand can do a full solo clear in 3:01. Please watch this video to understand how to do Brand's early jungle clear.

https://www.youtube.com/watch?v=FpjOVSB47Z0

The most important piont is that you can 3-proc your passive at lvl 2 to do more damage to your camps.

It's much easier to understand if you watch the video, but I'll try to explain it here.

Start the game by leveling Q. Kite the blue around with Q and autos, then smite it at the end. Level up your W.

From there, go to groomp. Q the gromp, then when your Q is between 5 and 4 seconds, hit W. Keep autoing in between. Spam your Q so that just as it comes back up, you use it on the Gromp again. If you did this properly, you should have 3-proc'd your passive, and you should deal additional damage to gromp for a faster clear. This can also be done on wolves.

Once you hit level 3 and level your E, it should be quite simple. From there, just make sure you consider getting your 3-proc off on every camp.