Light Blocking Techniques

I would agree with Don's suggestion of an aluminum/silver color paint.

I would think that to keep costs down you could use a silver spray can from a big box store instead of  using your more expensive model paint.

 In the case of close tolerances to some component where paint/masking etc. is impractical, perhaps you could use a silver ink marker, usually available in sets (with other metallic color pens) in many stores- I got some at the 99store

HTH

Are there any paints that would do the same job? I have some rather unusual pieces that have little to no tolerance for foreign objects when put together.  I have some aluminum tape that I will most likely use for certain areas of the model but it won't work for all areas. 

Thanks guys.

I use aluminum tape. Sold in rolls kinda like "Duck Tape".

I got mine at Lowes in the department with metal duct work.

Aluminum paint is best for blocking light.  They use a coat of aluminum paint on fabric aircraft to keep the UV from getting through the color paint and damaging the fabric. The fabric is clear doped first, then the aluminum, then the color.  Takes very little aluminum to completely stop light.

Sometimes it can be paint, but to block brighter light sources, one may have to use something like metal foil. Just be careful not to short your wiring on it if you do use it.