How to Shave Your Armpits Without Getting Bumps

Whenever I shave my armpits, I expect to do a lot of care-free arm raising like the women in razor ads and summer stock photos. In reality, I never throw my hands up in the air or wave them because I always end up with a bunch of tiny bumps on my underarms. I make sure to regularly exfoliate and don't shave everyday to prevent razor burn, but my armpits still have a cactus-like texture that's also slightly discolored from the rest of my skin.