I use a combination of heat shields:
1. Prime the inside with white epoxy primer.
2. For the large area, I use the nice adhesive backed aluminum from Van’s, but in areas close to the exhaust pipes I sandwich in 1/8” Fiberfrax (the same stuff I use on the engine side of the firewall) between the inside cowl skin and the adhesive backed aluminum. This stuff: https://www.aircraftspruce.com/catalog/appages/fiberfrax.php?clickkey=7985
If you look close at the photo you can see where the Fiberfrax under the aluminum foil. The Fiberfrax is in patches, first taped in with aluminum tape to both hold them in place as well as something for the cowl foil to stick to.
3. For the one or two real close to exhaust pipe stuff, I add these: https://www.aircraftspruce.com/catalog/eppages/exaustheatedshield.php?clickkey=39258
4. The control cables and wires under the engine are run through fire sleeve.
Shadow the pipes with fiberfrax. Don't need much area. Adhesion of the Vans self stick foil is best on a finish painted surface, which is also the most durable/easily cleaned. I do recall one fellow blocking his cowl exit with a section which came loose from a less prepared surface.