I juse them a lot - for strenght and "accid training" of the forearms (sorry i don´t know the english word).
The Danish Stickfighting Team uses a training drill up to any mayor tournament:
Take 3 kinds of sticks; 1 light material (like plastic and hollow) 1 regular arnis/escrima stick and 1 kamagong (thick)
Start with the normal stick and do Karenza/twirling for about a minute or two, then shift between the light stick, the kamagong and back to the normal stick while doing Karenza/twirling. Take an eggclock and turn it to lets say 5 minutes and do your reps.
Or another drill for body mechanics; take different FMA weapons, but make sure they go from short to large. Like a knife, Bolo, Stick, heavy sword and Bankaw/Bo-staff.
Then in front of a mirror or with a partner, make the correct body mechanics and shift between weapons - using the kamagong for the heavy weapons.