Hi, and welcome!
Apart from the mentioned tips on following the manufacturer's recommendations on what equipment to use, if your Echo isn't already a light color applying a white vinyl film to the roof would reflect more heat. That should keep the inerior cooler and reduce how much you need to run the air conditioner. Similarly a dark tint on your windows would reduce a hot cabin and therefore the cooling demand on the A/C.
I would recommend the driving technique "driving without brakes" (DWB). Do not take that literally, but more as a reminder for the following: Every time you push on the brakes you are wasting the momentum of your car, thereby converting your money into heat. So look ahead, time stoplights so you don't need to come to a complete stop, give people more room, give yourself a few extra minutes time to drive so you don't need to rush.
Good luck with your pursuits!
