Hello Myoneandonly! (such a charming "handle!)
We seem to sell a good little bit of the RL Metallics where I work (also sell a BUNCH of RL wallpaint too!).

The RL metallic is a "subtle" look for a metallic. The Modern-Masters brand is more shimmery. Do you know if the powder-room you saw had the RL in it?!

RL metallic is kinda "borderline" for bathroom use, i.e. not much sheen to resist moisture. DON'T use it in a main bath...UNLESS you apply 2 coats of a Dead-flat-varnish. We have this product too...unfortuneately it's $55/gal. I've found out that a good quality latex varnish that's FLAT isn't cheap!
>>> MAKE SURE you get the RL "stringy" roller for your metallic though!
>>> With a traditional roller, the metallic just pools too much. The stringy roller mottles the edge. Do the light top-to-bottom "sweeps" of a section too...to even out any ridging!!
>>> Start with a primer! If a deep metallic, use a gray primer.

Faron

Ty Faron for answering. It was indeed RL metalic in the powder room. In a house that had pale yellow walls and traditional moldings, it was quite a surprise to open the powder room door and see that gorgeous paint. You certainly sound experienced and I appreciate your advice. If I can get my nerve up, I'm going to do it, using the stringy roller over gray primer as you recommended. I love this forum.

Thank you Myoneandonly for your kind note!

Additional notes...
I did a small "demo-wall" in our store with the RL-Metallic. TWO coats mandatory.
* I LIGHTLY rolled over the two dried coats with a little of the paint thinned slightly with water.
* You could use a Glaze-mix too...VERY LIGHT touch here, and roller almost dry.
* It gave a slightly more "mottled" appearance. I was kind of experimenting! Try your version on a primed piece of cardboard or foamboard.

Faron