There are different kinds of spatula and putty available - depending on the aim you need to get the right one.
Elastic putty are ideal for plastic and metal parts, but also further surfaces can be worked with it. Fine putty leads to smooth, poreless surfaces. Filling putty is used to even out uneveness like dents on the chassis and materials that are made of metal, stone, concrete, plastic, ceramic and wood. Combination putty is better for smaller uneveness and for sealing pores.