We have a house that is painted in identical color inside and out - kind of a sage/camo green color. What looks pretty nice on the exterior is a bit dark inside - but particularly so in the basement. Over the past week I painted one bedroom downstairs. It took two coats of primer and two coats of paint over that to cover the green with a warmer buttercream color that brightens the room considerably. However I still have a ton of basement remaining, as well as the main floor. And doors. It's an overwhelming job.
So... I bought a spray painting machine. It says it's for the "entry-level contractor". Hopefully that will work for an experienced but ovewhelmed home-owner :)