Double LeiG is certainly the way to go - the "Ready for Another Round" 25% Reduction on Barrage Cooldown Bulletin helps a lot too in this regard. The key to Brits is pressure pressure pressure - keep forcing him to Brace and don't give him time to repair. Have a Raketen on standby once you see he's braced - once it wears off attack and the emplacement will go down quick.
If he has a lot of Emplacements consider using the Fortifications Commander and build a LeFH Howitzer and use that. If you can bank 300 Munitions then Zeroing Artillery also is very good too (keep in mind you need to keep vision for it to work).
