I often get referred to homeowner through the RL help desk at 800-379-POLO. Most of the problems using the River Rock and Suede paints is that folks try to apply them like a flat latex.
To cut in, RL sells a mini textured roller. First, you MUST be generous with the product. Yes, it is pricey, but overstretching will work against you. Lots of paint is needed - as it states on the textured cans, one gallon only covers half the area that the non-textured paints do.
Don't cut in the entire room and then try to use the big textured roller to finish. Cut an area, then roll it. Use very light pressure on the textured rollers. Don't push hard or you'll get edge build up. Another problem is that many ignore the "dry roll" step. When done a segment, you need to do the "floor to ceiling sweep" without dipping your roller in the product first. Again, a light touch is the secret.
The first rolled coat will look nasty - I warn clients in advance so they don't freak and think I don't know what I'm doing. The initial coat will look spotty and uneven. Ignore that; the second coat will cover beautifully.
Unless doing the one-coat BRUSHED Suede technique, you don't have to use a flat paint first. Yes, as with any paint job, you need to evaluate what is currently on the walls and properly prep. This may well entail a primer (untinted) is you're going to paint over "builder grade" or a very dark color with a light one. But that isn't dictated by the RL textured products; it is just standard prep.
My site shows and discusses some other RL products, www.enlivened.com, if you're interested.