Halo Reach has a BxR too! Watch this video and learn how it is done.
How to BXR in Halo: Reach | R, R+Y, B Button Glitch Tutorial w/ CommentaryAlso I have not found any videos on these following tips yet. But another trick is called "sprint cancelling"
Sprint Cancelling eliminates the delay between throwing a grenade and shooting, and melee'ing and shooting, and melee'ing then melee'ing.
How it is done:
Simple!
-Grenade, sprint, sprint, shoot.
-Melee, sprint, sprint, shoot
-Melee, sprint, sprint, melee
Note: In order to "sprint cancel" you must being moving forward (this movement allows sprint to be used)
Enjoy!