no experience with carrying drums, but sounds like a lot of back and core strength. cardio doesnt really seem like it plays a huge role here (im guessing you dont run in drumline?) but im guessing itll still help some. i would for the most part suggest a whole body resistance workout. things like lat pulldowns, pullups, curls, rows, deadlifts ect, and anything that works your core. muscular endurance seems like its gonna be key here, so even if you cant practice carrying around the drums, try going for jogs with ankle/wrist weights before every workout maybe? my friend who was in marching band always worked out his calves and said that helped with marching, so calf raises and stuff wouldnt hurt eithera good diet to accompany this wouldnt hurt either
high-rep low-load stuffdeadlift to upright row, lunges, pullups, loaded russian twists, no-leg planks, etc. just recognize what muscles start aching when u walk around w/ all that and do lifts and exercises that work them
i used to lug my friend's quads around, and it wasn't that bad tbh.