No, you don't need to tape the inside of the canopy - I believe Wojtek was referring to the interior colour of the frames, visible inside due to being on the outside first.
Once masked, paint this colour first, allow to dry thoroughly, then paint the exterior colour. This will then show the interior frame colour inside the canopy.
I presume that, by BBMF, you mean the Lancaster?
Another way of doing it, although slightly time consuming, can be a little easier, and more accurate in this scale.
Lightly place a length of clear 'Sellotape' onto a sheet of glass, or similar smooth, clean surface. Paint the strip with the interior colour, allow to dry thoroughly, then paint the exterior colour.
When fully dry, and using a straight edge as a guide, cut strips of the required width, but longer than required, and carefully peel from the glass. Place over the lines of the canopy frames, press into place, and trim off as required. Then carefully burnish down to seal. These can be sealed in place, if required, by a coat of Johnson's Klear' (Future/Pledge with Klear) and, once dry, the frames can be touched - in with a clear matt coat, using a 000 brush.
It sounds complicated, but is very simple, and extremely effective, and a lot easier than trying to mask the turrets, in particular. It works better with enamel paints, as those toy town acrylics, although they'll work, are not as resilient, and may crack easier when peeling or placing the tape.
Hope this helps.