TGUs, windmills, and presses help your lats and obliques deal with carrying snow on a shovel.
Nothing really helps specifically for bending down to pickup the snow although it is better to bend at the hips, not the waist.
If done right, with a full shovel of snow and locked arms (left hand at the bottom of the shovel and right hand at the handle) and tense, flat back you can explode up as if doing a swing and kind of point the snow in the right direction. This takes a lot of stress of your back and uses your hips and glutes. For me, it tends to hit the hips a little more than the glutes though. My hip flexors are a tiny bit sore today but that’s it.
Any other hints from more experienced snow bound types?

