My favorite thing to do with customers on the fence is instill a little doubt in my competitors process. I’ve had customers say “well I had it done cheaper last year” and I tell them.
1 You won’t need it done yearly with my process then answer the question “why not” (and it’s not a lie. In my area houses don’t get algae buildup as quickly as others)
2 My process is safer for your home and won’t damage it.
3 if the other guy damaged anything or doesn’t do a quality job let me know.
I usually only get step 1 out of my mouth before they change their mind.