Testors has created a product to help in the aid of decal application. These products work very well in helping set and place the decals in the desired position. The solution can be used on most surfaces. Decal Setting Solution is used for decal placement over panel lines and protrusions, allowing the decal to stretch and conform to irregular surfaces.

Setting Solution also allows you to move the decal after you have applied it to the surface, for precision placement.

Apply decals to model as directed in instructions.
Blot dry decal with soft cloth, making sure to press out air bubbles.
Apply Decal Setting Solution with small paintbrush, spread evenly! Let dry.
You may reapply repeatedly if necessary, until the desired result is obtained.5). It also works well for removing decals.

Apply liberally and let soak in for a few minutes; once decal softens, remove