I cannot see how anyone can scrim the edges with a damp cloth and NOT leave smears.
If you've been doing it for thirty years it's easy. If your scrim is dry or very slightly damp, you detail after you've bladed. If your scrim is to damp and not drying (ie: in colder weather or in light rain) you use your aplicator first followed by your scrim to soak up the excess water round the edges which takes enough water off the edges to allow you to blade the rest off without having to detail after. I've used this method for years and it leaves as good a job as doing it the other way round (ie: Detailing after blading). It allows you to work in light rain and if you keep a new blade in your squeegee, you'll seldom leave lines.
Incidently, this only works with a well wrung scrim, not with a soaking wet scrim.
Working in light rain is not a good idea though if you haven't had rain in a while. There'll be a lot of dust/muck in the atmosphere that'll be in the rain and will mess up your work and possibly cause problems with your customers.