I love model RR. I started with an N scale then moved to HO but ran out of room. It's a fun hobby and love those Kd couplers.
I hope I don't confuse you but this is how I paint the molded details in the seat. By the way that F-106 is the old Monogram mold and an excellent one too.
I like to airbrush the base coat to avoid paint build up that usually happens when hand brushing if not careful. I spray the enamel OD let it dry. I then use a small brush and lightly and carefully paint the belts. Try using a light grey or light green instead of white. Once dry, brush a light coat of Future to gloss up the area in preparation for a wash. Since Future is acrylic it acts as a barrier against the enamel base coat. I let it dry a couple of hours then mix some artists black oil paint and thinner to make a wash which is applied with a thin small brush as a pin wash. The gloss will let the wash run in a sharp fashion outlining the belt, creating a shadow and giving a 3-d effect. If the paint is flat, then it has a tendency to wick a little and you may not get a sharp wash line. Let it dry a couple of hours then shoot some clear flat.
Here's a great site, just scroll down for the seat:
http://www.flickriver.com/groups/1625718@N25/pool/interesting/