Many people have a problem when painting surfaces with too smooth or too uneven relief. In fact, the secret of painting such surfaces is very simple. First you should disassemble the painting of smooth surfaces, the complexity of their coloring is that the entire paint flows on the surface or lies uneven.
So that this does not happen, you should degrease the surface, and add a little hydrochloric acid to the paint. If you paint a smooth surface with spray paint, then hydrochloric acid can be applied to the glass itself, just do not overdo it differently, the paint may come down. Now we will deal with painting surfaces with an uneven relief, here it is actually not so easy to paint, since the paint flows into the recesses and because of this the object looks very not beautiful. You can solve this problem by painting the surface with a thin layer of spray paint, if possible, be sure to degrease the surface.
If the surface is steel, then you can paint it with machine paint, since this paint falls on the metal more even more than others, and if wooden, you can use ordinary paint, but apply a thin layer and several times.