I have this morning separated Mike Schorsch's excellent marching percussion additions to the TimGM6mb soundfont into it's own soundfont for use with MuseScore 2
If you want to use instruments from the new Marching Percussion Instrument Group you will need to enable this soundfont in the Synthesiser page.
You can download it here:-
http://www.filefactory.com/file/7dl5l7zuzxtf/n/MikeScorschDrumLine_sf2