… (i can always pop a rock or two into the bottom of my brothers pack if needs be).
The tricky part is that a rock attached to the feet is different from a rock in the pack. That is, it uses different muscles. So it requires different training stimulus.
If you’re going to do a ski tour, you’re going to be climbing with lots more weight on your feet than normal dryland walking or running. So as the time of the ski tour approaches, you need to train specifically with more weight on your feet. Which typically means if you live near snow to do some climbing up with your actual skis+boots+bindings+skins on your feet. Or if you don’t live near snow, than practice with ankle-weights on your feet - (likely even better if find a steep hill, or stairs).
Same principle as if you’re going to be carrying a heavy backpack for a multi-day trip, you do better if you prepare for it by training carrying a pack with weights or water in it.
I tour with heavier skis + boots + binding, but because I train ahead for it with ankle weight, I’m faster climbing up on skis than lots of people who paid extra for fancy lighter skis, but didn’t train specifically.
P.S. Getting serious about acclimatization to reduced CO2 pressure at altitude also makes a difference for some trips.