As with exterior painting, preparation is very important. However, often with interior there is less dust & dirt on the walls and therefore not as much time is needed on preparing the walls. However in fully furnished houses the preparation, including the removal and re-hanging of curtains can take almost as long as the actual painting itself.
SPECIAL ATTENTION AREAS
Specific areas that might need special attention as far as interior painting is concerned, is areas like the kitchen where food is prepared. There often is a bit of a grease build up in areas in close proximity to the stove. These areas should be cleaned properly with a bit of sugar soap before repainting.
Ceiling areas in bathrooms where damp cause bleach fungal growth on the ceiling should be cleaned properly, and treated with an anti fungal. Black marks can be obliterated with road marking paint, before repainting it. This is the only instance where I will recommend a paint with a sheen for a ceiling as it can prevent future fungal growth.
Ceilings should almost always be painted with a matt product as any sheen product will highlight imperfections. As a ceiling is not a “high traffic” area there is no need for a high quality paint, however it should be of an acceptable quality.
Gaps between the wall and the ceiling & the cornice and ceiling as well as around the door and window frames should be cleaned out properly, before being filled with an flexible acrylic sealer like Painters Mate (not Polly Filler).
Interior walls should normally be coated with a washable product for obvious reasons. The higher the sheen of product, the more washable and scrub-able it normally is (not always). However a high sheen product not only highlights all small plaster imperfections, but normally does not give a aesthetically pleasing finish as it looks a bit like a hospital. I have to add for high traffic areas like hospitals, vet’s, schools and day care centers, and lower cost houses, specifically when they are rented out, a higher sheen product would be the most practical. However for any average residence a quality washable matt , low or mid sheen product, will be best with a low sheen pure acrylic (the best option in most cases) but definitely not all. Low sheen pure acrylics gives the client best of both worlds: a durable & washable finish that does not highlight imperfections.
Likewise it is better to paint indoor woodwork with a Eggshell Enamel or an Thixo-gel low sheen enamel than with a standard High Gloss enamel.
I personally prefer a timber preservative for most natural wood as it does not simply form a coating over the wood like most varnishes, but seeps into the wood and nourishes it, and often brings out the natural textures and colors in the wood. There are areas where a varnish product works better, specifically when you need a hard protective coating like a poly urethane varnish. Ask the person doing the quote to discuss these options with you to see what is better for your specific application.