You can choose from several different products if you want to install a bed liner yourself. The herculiner bed liner kit is one of the most popular choices. My neighbor recently coated a truck bed with this product, a roll on bed liner, and here are my observations on the results.
First of all, the paint comes in a bed liner kit. You can buy just the coating in gallons or in quarts. The gallon size is not quite enough for a full size pickup either. But the kit has most of what you'll need to do the whole job. So you can get everything at one stop.
Color choices are another plus. You can choose the standard black plus red, white and gray and maybe other Herculiner colors by now. So match the bed color to the color of your truck.
My neighbor's truck is an older pickup with a bed in pretty good shape. Just like any paint coating, preparation must be right or you'll be looking at a peeled finish. Sand the bed very hard so the coating can stick. And before sanding, clean the bed so there's no wax or grease that will keep paint from sticking. Now preparation is really quite easy ... just clean and sand.
The material is very thick. There's a very rubbery texture in the coating so it looks much like a spray on liner once you get it on. Make sure you stir very well because it is thick and you can have some of the texture left in the bottom of the can.
Applying the paint is just a matter of rolling on the very thick coating. You can apply two coats so you can miss a few patches on the first coat and catch them on a second coat. If you have a long bed you'll probably need at least 5 quarts. A gallon isn't quite enough, so buy an extra quart.
The thick coating will spread out a little after you apply the finish. That way any brush marks or roller marks will disappear. The final finish looks like it was sprayed on. Especially for older trucks badly in need of a spruce up, the Herculiner kit is a cheap way to protect the bed and make it look better too.