Given that the Germans used so many pillboxes on the Salient, did the Army Battle Schools teach how to defeat them? If so, does anyone have acopy of the "drill" that they used

Delta

The two most important were training pamphlets on this subject were S.S. 143 Instructions for the Training of Platoons for Offensive Action and S.S. 144 The Normal Formation for the Attack. The former (a “vital milestone in tactics” according to Paddy Griffith) marked the transition from tactics based on the battalion and company to a platoon-centred approach to minor tactics. S.S. 144 provided practical examples of how these new platoon-based tactics might be used.
These two pamphlets enabled the BEF to develop a successful drill for the suppression and capture of the pillbox (or mebus) - a key element of many German defensive positions in 1917.

For tanks, a drill was developed for them to work alongside the infantry in this role - I can give you more details if you want. You can get copies of many SS pamphlets from the Imperial War Museum's Dept of Printed Books.

Hope this helps

Bryn