Bob,
Most panel lines on the fuselage and wings on the Me 262 were filled with a metallic colored paste and filed and sanded smooth.
Some artists illustrations in older Me 262 reference books have the filler putty a tan or wood color and this is incorrect, the filler putty was made to match bare metal surfaces because the RLM wanted to eliminate painting the lower surfaces of their fighter aircraft to lesson weight, use less material, and reduce labor costs. That's why some very late production Bf 109's, Fw 190's and Me 262's were seen without paint on the lower surfaces in photographs taken shortly after the war ended. Wood, steel, or fabric surfaces would still get painted.
The Me 262 was clearly a high speed aircraft and having smooth surfaces on the airframe was important to reduce drag but even though the filler putty was used the poorly skilled slave labor often left the surfaces less than smooth from poorly aligned metal panels or filler putty not sanded down properly.
I have built a HobbyBoss Me 262 and I thought its nearly as good as the Tamiya kit, the surface of the plastic was not as refined but that did not detract from the quality of the finished product. If I could buy more HobbyBoss Me 262 kits I would, the BMW 003 engine version is of great interest to me.
Matrixone