What kind of regimen can be used after Kenalog injections to prevent fat atrophy or dents?

I have been injecting intrasional steroids for treating hypertrophic scars, keloids, cystic acne and other inflammatory conditions for well over three decades. Injector experience, and appropriate level of injection, as well as choosing the right concentration and amounts are the best ways for reducing the risk of steroid injection atrophy. The use of topical retinoids and microneedling may help for a very superficial depression should it occur, but are unlikely to be of any value in preventing its occurrence, as are all the other things you mention in your question. Happily, should it occur, steroid atrophy often spontaneously resolves in several weeks to months. If needed, saline injections may help to speed the resolution, as can fillers. Make sure that you are consulting with an experienced board certified physician. Best of luck. 

Fractional laser with PRP SC can help reduce atrophic skin and soft tissue risk. The most important is to advise the surgeon not to administer high doses of kenalog. I would suggest massaging the scar with a polysiloxane scar gel. Best, Dr. KaramanoukianRealself100 Surgeon