To minimize filling and sanding my models’ joins, I use the plastic lids from takeout drink cups or the lids from ice cream tubs from a well-known burger chain.
These are thin enough to make shims and can be built up to the desired thickness to fill a seam. They can then be trimmed down to suit, since some models do not leave a lot of leeway when joining fuselage halves. I also find the thin plastic is ideal for use on wing-root joins, which I find are often the most awkward places to fill and sand.
Tip submitted by:
Tony Ward
Bridlington, East Yorkshire, England