When repairing dents, the first task is to stretch the deformed surface in order to bring it back to its original level. Attempts to achieve one hundred percent correspondence to the original do not make sense, since this is still impossible due to the violation of the internal structure of the metal of the body panel upon impact. Optimal is to bring the concave surface to a level of approximately 3 mm below the surface of the surrounding undamaged area of the body panel. If the dent isn't deep, pulling it out completely doesn't make sense at all.
In the case when the concave area can be reached from the back of the panel, you should try to straighten the dent from the inside by hitting a hammer with a soft material striker (rubber, plastic). While tapping out the dent, firmly press a wooden mallet against the face of the dent to dampen the shock impulse to avoid excessive outward bending of the deformed panel metal.
If the indentation occurs in the two-ply section of the panel, or otherwise cannot be accessed from the back side, a different pulling technique must be used. Make several small holes in the concave section of the panel, trying to ensure that they are in the deepest areas of the dent. Then screw long self-tapping screws into the holes, leaving their heads sticking out enough so that they can be grabbed with pliers. Now start pulling out the dent with tongs behind the screws.
In the next stage of treatment, the dents should be removed from the damaged surface and in an area approximately 3 cm wide around it, the remnants of the paintwork. This work is best done with a wire nozzle or a cleaning disc mounted in an electric drill chuck, but manual sanding is no less effective. The final stage of preparation for puttying is scratching the dent, cleaned of paint, with a screwdriver or a piece of file, or drilling small holes in it to ensure maximum adhesion of the putty to the metal surface. Then you can proceed to the implementation of the procedures of puttying and painting.