Lastly, chose a sheen to match the needs of the space. Flat finishes hide imperfections well and absorb light which can make the paint look darker. Eggshells and satins are tough enough to be used in family rooms, kids' rooms, and hallways but don’t hide surface imperfection well. Semi-Gloss and high-gloss finishes are primarily used for trim because they accentuate woodwork details and clean up easily.
• One room or the whole house? Applying one coat in one room is a reasonable DIY Saturday project (especially if you have help and beer). Multiply the time spent moving furniture, prepping walls and sanding old trim by the number of rooms in the house, and you might want to hire real help. It's the same outside. You can probably tackle one shady garage wall that needs a little scraping and sanding plus a coat of paint, but covering all surfaces of the house is usually best left to a pro.
Denver House Painters of Colorado