My favorite is lactic peels combined with Radiancy LHE microphototherapy. I also like to use the Brightening Infusion Mask by DERMed, out of Atlanta, but I believe they are discontinuing that mask in favor of a milder version called Brightening Mask. Similar ingredients, but much too mild for my taste.
My ideal treatment would be:
Cleanse and tone with Dermed Brightening Cleanser and Toner
Allura Esthetics L20 Pre-fin (a mild Lactic acid peel)
Radiancy treatment, ideally 2 passes of 5-6 pulses per spot, or whatever the client can handle
Brightening Infusion Mask
Remove and apply Hydropeptide Serum and Face, plus SPF if it is daytime, and the client will really need to commit to SPF in that area. I have recently added some of the COOLA body SPF's to the lineup - they're great, not sensitizing, smell like high-end body lotion, eco-friendly, and nice packaging.
I am also experimenting with Mlis Tissue Repair Cream for after strong treatments. I've tried it a couple times on my face and broken out, but I'm very acne prone, and I think it might still be suitable for the type of sun damaged chest skin you describe.