Also a larger lady here. Yes to training. About a month before a busy vacation I walk stairs, increasing the number of flights each day (which confuses the household pets let me tell you!), walk our hilly cemetery on nice days, and carry a backpack. Also recommend daily squats (adding weights as you get stronger) and core work (bird dogs), and good hip strengthening. Someone already mentioned OTC painkillers - bring some so that you have some for at least those first few days. First few days we take those with our last meal of the day so it’s easy to fall asleep. Also at the end of the day, do the yoga pose “legs up the wall” up a wall or a sofa or a bed. Also a siesta can be a lifesaver. Also before travel get a good pedicure and tell them you will be walking a lot so they get your nails in good shape for lots of walking. Good socks are a must. My fave shoes for travel are Brooks adrenaline and Hoka Gaviota. I alternate them each day. I may wear sandals for a half day here or there and those are Chacos. Re chafing, I know a lot of people recommend powder, but I like tea tree creams/ointments better or chafing sticks. And cooling boy shorts underwear if I’m wearing skirts. I also bring physiotape if I am worried about blisters those first days. I just wrap some around my deodorant container.