Lightmap scale directly affects how many lights a texture-light emits.
It might be due to the size of the block you are texturing that a small change won't have a change due to how the size of the lightmap scale grid fits on the brush. Try going smaller.
2nd thing is that they won't exactly 'glow' and just radiate ambient light, you need a nearby surface which can lit up by the texture. I've found texturing directly on the floor will always look dull because there's not much for it to light, whereas if you use a strip bordering the floor you can get a much more noticeable effect. If you want to do the floor, consider putting it say in a recessed area with a glass strip over the top and it might be much more prominent.
Also I don't know about RNC but I used like a brightness from 300-500 for my recent indoors glowy map. That map had like no other lighting however.