Another trick is to drill a hole in a 2-thickness interior panel area or a roof support that will allow a curved rod to be inserted under the dent and apply some upward pressure to the dent while tapping around the damaged area with a body hammer or a slapper. The hole can either be patched later, or covered with upholstery where that's an option. Snap-On used to sell a set of curved dent lifters made of spring steel called "pick tools" to reach hidden dents, but they tend to be horrendously expensive antiques these days.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!