Hey congratulations on your upcoming surgery! One month from now, it will be done!!
I didn't have Double Incision, I had Peri but this might help... the not lifting arms part is so that scars don't stretch out. Initially, there might be some pain with that too. To avoid having to do this, start thinking about your home space (or where you will be recovering.) What kinds of tasks in your home have you normally raising your arms? Getting dishes out of a cupboard, getting something out of a closet, etc. Get your place setup so you don't have to do that reaching.
I don't remember how long I was to keep from showering, it wasn't too long, a day or two? And then with first showers back, I had to avoid having water splash directly on the bandages. With Double Incision, you have to wait to shower until the bolster dressings are removed. Some people find "dry shampoo" to be helpful.
Your surgeon should provide you with detailed post-op instructions. Sometimes the info is contradicting because surgeons have different general guidelines or because one patient's healing process can be different from another's experience. I remember thinking, wow my surgeon didn't tell me do do that! then asking the surgeon and getting a totally reasonable explanation for why my instructions were different.
Dr. Mosser has a great page on his site that outlines what recovery is like, check it out here:
https://www.genderconfirmation.com/techn...r-surgery/
There are also a few pages about preparing for surgery here:
https://www.genderconfirmation.com/pre-s...-care-ftm/
Good luck!!