This is one of the easiest and most durable surfaces to paint. If there is chipping or flaking of the old paint, prepare by using a pressure sprayer. This will avoid creating airborne dusts and will clean the surface nicely. Today’s 100% acrylic (latex) paints are ideal for this surface.
I recommend that you apply paint using a high quality airless sprayer that you can rent reasonably. Brushing is fine, but will take longer. Talk to a local paint store such as Sherwin Williams, Kelley Moore or Benjamin Moore. They will have be best quality paints and can help you with suggestions whether priming is recommended. Most likely, this siding will not require priming if fading is the only problem. Be sure to ask for a preferred customer discount. Most of the pro paint stores have several retail price schedules, and if you ask for a preferred customer price, they will gladly give it to you to earn your patronage.
Post back if you have any other questions, and good luck.