I wanted the liner to cover part of the top of the sides, so masked the area off and then removed the tailgate. That was easy to do and made painting the tailgate much easier. Applying the DIY paint on bedliner consisted of rolling it on with small paint rollers supplied with the kit. Corners and small areas required "daubing" paint in with an old paintbrush. The truck was allowed to sit overnight and a second coat applied the next day.
I checked out the preferred bedliner (at least in my area) - a Rhino Liner. At around $400 and up it was beyond my reach. A Line X bedliner is also available, but also spendy. Auto parts stores sold several do it yourself spray on liners, but I was not impressed with any of them. An on line search yielded a paint on bed liner made by a company called grizzlygrip. It appealed to me, and even came in many different colors and I eventually purchased an application kit.