I would like help with Power leveling

Hey all

i need help to Power leveling. What is the best place to do it if i was to do it solo or if i can to it. I’m on PC using steam with all of the DLC. I have a lvl 52 Commando and a lvl 12 gunzerker that i would liked to be maxed to lvl 72

my steam name is Immortails920

if anyone can help me boost lvls message me. Thanks