The way you paint your bathroom is similar to how you paint any other room. Apply a coat of primer, cut in around the corners with a brush and then use a roller to cover the rest of the wall. The thing that is different about painting bathrooms is the type of paint that you use. Functionality of the paint is more important here than in any other room so you need a paint that is durable, water-repellent and inhibits the growth of mold and mildew.
In most cases a latex enamel will be sufficient for your bathroom and shower walls. Choose a semi-gloss or high-gloss paint rather than a flat or eggshell; the glossier your paint is, the better it will be at repelling water. Also be sure to prime your walls before you begin painting to seal the wall and provide extra protection against moisture, mold and peeling.
Oil-based paints are also effective for painting your shower walls but they are more difficult to work with than latex paints. They are naturally better at repelling water but they take longer to dry and produce a strong odor; so you will need to keep the work area well ventilated. Clean up requires the use of solvents and paint thinner instead of just the water needed with latex. Also, when the time comes to paint again you will have to use more oil-based paint because latex does not adhere well to oil.
Specialty Bathroom Paint
Paint manufacturers also produce a paint designed specifically for use in bathrooms. These paints include chemicals that kill mold and mildew and help prevent their growth. This is especially helpful in bathrooms with poor ventilation, but is often not necessary if you have a strong fan and keep the bathroom door open after showering.
Painting Your Shower Surround
Perhaps you want to paint the fiberglass surround in your shower. This can be done with any of the paints mentioned previously as long as you take the right steps to prepare the surface.
First, sand the fiberglass with an extra-fine grit sandpaper. You are just taking down the sheen and giving the paint a place to stick. Second, clean the shower surround with a cleaner to remove excess dust and dirt. Third, rinse the shower surround with water and let dry.
When you are ready to apply the paint use a sprayer to avoid the appearance of brush strokes and achieve a smooth finish. You can use either a couple cans of latex aerosol spray paint or a paint sprayer to receive long-lasting results.