Johnstone silicone enhanced render 1.5mm

[Rustysul]

Hello, just had front of my house rendered with Johnstones silicone enhanced render 1.5mm, then I had the exterior brick sills painted, but next day had heavy rain and either the paint has run or dirt & grime from under the sill has marked the new render. What is best to clean these marks away without damaging or spoiling the finish, your advise is much appreciated.