It's always best to completely strip off any previous waxes/sealants/dressings for our products to last and perform to the best of their abilities.
Dish soap will in no way harm your vehicle. There are many rumors on the internet about it potentially being harmful to your vehicles rubber/plastics, but there is no scientific evidence or research to support these claims.
We have used dawn soap for many years for clay lube, prepping a vehicle for wax/sealant or for cleaning rubber and plastic surfaces in preparation for our Plastic Restore/Shine Dressing products. We have had no adverse reactions to any of the vehicles we have maintained over the years.
But of course, if you don't want to use dish soap, there are specific 'strip car wash' products. Dish soap just does the same function without spending money on additional products. If you search "strip wash" on Amazon you should be able to find some products.
You can also still go ahead and use regular car wash soap and apply our product and you should still have great results :)