Reducing size and excess skin on upper arm

I am scheduled for WLS on August 11 and I am trying to get a jump on exercise before and I have very large upper arms.  Please share advice on reducing size of upper arm and any tips related to how to reduce the dreaded "flappy arm"... I know there will most likely be extra skin, but any methods to reduce would be appreciated!

Pushups! I do 100 a day, sometimes spread them throughout the day. Pullups and dips (I do them on the machine at the gym that assists you), and all the machines at the gym that are for arms. The ones that focus on triceps seem to help mine the most.