Car wash

THis afternoon I went to the car wash again with my fiat500 cabrio. The roof is impregnated but... it is not recommended to do this. But washing my car myself, isn't an issue anymore.. too heavy.. with my back issues etc. But at the car wash they also have a program you can choose, that you wash the car yourself.. so.. next time I will try that. Never did that before .... anyone tips?
Anyway... my "bolletje" is fully clean again.