In my younger days I once worked as a painters helper, I learned a lot about paint, paint brushes and paint rollers so I got a few tips to share. I had to get a little help from my old boss first to make sure I got this right.
How good is your child's bedroom if you put in new bedding sets, curtains, pillows, decor, and accessories if the paint job is not just right? The basic rule for easy, efficient painting is simple, use a roller whenever you can and wherever you can. A roller covers these areas more than twice as fast as a paint brush and requires less skill and effort.
A roller alone, however, will probably not get the whole job done. Most interior painting calls for both the roller and the brush; as a matter of fact a single brush may not be enough for the best work. You need a brush for surfaces that a roller is not designed to cover, a delicate, ridged molding for example, or the narrow divider between windowpanes. You also need a brush, not necessarily the same brush, to use in corners that a roller can not reach. And you may want to use a brush to paint certain flat areas, such as the wall above a shelf where working with a roller is awkward.
Choose a brush of the right size and shape for the kind of work you are doing. Use as wide a brush as possible, to make the painting go faster, but not wider than the surface you are covering. A 1 or 1 1/2 inch trim brush is good for window dividers, a 2 or 2 1/2 inch sash brush for baseboards and window frames and sills. For large flat areas use a 3 inch or at most a 4 inch brush. (Professional painters regularly use 4 inch or even 5 inch brushes, but it takes long practice and a powerful wrist and forearm to handle them with ease.)
Choose a brush shape that is tailored to the job, the familiar flat brush with squared off ends is a general purpose brush, for precise edges and lines, pick a flat trim brush with a beveled, chisel-shape working end. An angular sash brush, especially designed for certain hard to reach surfaces, can not normally be used on flat surfaces but is ideal for inside the window and door frames. Round or oval brushes have the largest paint carrying capacity and splay out when applied to a surface, they work best on thin, curved surfaces.
Finally, match your painting tools to the type of paint you are using. Latex paint, which is likely to be used for at least part of every job, calls for a brush or roller with synthetic bristles or nap. Natural bristles and fibers absorb water from latex paint and loose their resiliency. For oil or alkyd paints, which give a smooth gloss to trim a good synthetic bristle brush will do the job and can also double as a cutting in brush if you are using latex on the rest of the room.
I hope this little bit of information can help some one in making the perfect bedroom for a child.