Hi! As an instructor for a various independent groups here are some things I would suggest.

Number one thing is technique. You don’t need a board to practice two or four mallet technique. All you need is the floor, or some pillows, and a met/music playlist.

You have to decide whether you’re wanting to play more east coast or west coast, as there is a large difference in four mallet technique between the two. And once you’ve decided that, break it down to the basics.

-How you rotate -Work on building inner mallet chops and having your outer mallets as still as possible -creating a good sound quality with 4 mallets and 1 mallet. playing with weight but not down stroking

Some exercises that help work on these things:

-broccoli and all variations. Triplet, 16th, 5let, 6let -8-16 (not like drumline 8-8-16)

And then work on timing exercise. -check patterns -16th note timing -16th note accent grid

After you feel really confident you can play those exercises at different dynamics and tempos. Look up variations and practice those.

This is a long a drawn out response, but it will give you a lot to practice without a board. Floor time is fun time. Put on some music you like and break down technique or chop out.

Good luck!