Straightening
Smooth out small dents with a straightening hammer. In this case, you need to put a fairly massive stand on the other side. Don't hit too hard with the hammer, otherwise the metal may stretch too much and you won't be able to achieve a smooth surface. When straightening, you need to move evenly from the edges to the middle.
The surface to be straightened should be periodically checked by hand until the desired shape is obtained. Small irregularities can then be eliminated with putty.
Rusty places and remnants of old paint after straightening must be carefully removed from the repair site. You need to use coarse sandpaper wound on a suitable bar or grinder. Cover adjacent painted areas or plastic parts with adhesive tape so as not to damage them when stripping.