done a whole day yesterday of first cleans, it was a very tireing day, just take your time, scrub the frames and keep rinsing side to side/downwards, i very rarely get a complaint after first cleans now, just take your time and you should be alright.
The only thing that can be annoying is with white UVPC frames if there old, perished and stained then they need restoring, I've had a few complaints sometimes after cleaning these as restoring them is extra £££ and time