First, knock off the paint on the parts that need to be trimmed, smooth the concave and convex parts, polish the bottom with sandpaper, and apply putty for molding. The putty should be thin, and the concave part should not be filled at one time. After each treatment and polishing, the putty should be below 1mm for at least three times, and finally the primer should be sprayed. Then use metal putty to find trachoma, and then apply primer. After no trachoma, the topcoat is usually sprayed twice or three times, mainly depending on the color or viscosity of the car paint. Paint and enter the spray booth.