Sorry I'm a bit late to this discussion. I'm on sabbatical and part of my discipline is to ride more and surf the internet less.
IMO, "Flush & Drizzle" is only a stop gap until a proper service can be completed. Unless the freewheel is opened up, bad bearings, broken pawls, and corrosion cannot be seen nor corrected.
All new freewheels come with grease, not oil. In NOS vintage freewheels, the grease has usually evaporated. Depending on where the freewheel has lived, there can be internal corrosion on the bearings and surfaces. In 1990s Sachs Aris freewheels the grease normally turns into a very sticky "peanut butter" which can cause the pawls to stick close. The red plastic seals/bearing cages basically preclude "Flush & Drizzle" unless the sprockets are removed to access the port. However, let me caution I've seen old Sachs grease so caked into the pawl sockets that I had to dig it out with a tool even after a long soak in solvent and cleaning in an ultrasonic cleaner.
My preference is to use synthetic grease which is very temperature, moisture, and salt resistant. Those three properties work well together to keep contaminants from reaching the bearings, pawls and spring(s).
My rule of thumb is to only use enough grease in the race to hold the bearings in place. I place a drop of oil on each pawl pivot and I wipe the ratchet teeth with the same oil. Grease is a no-no in the teeth or on the pawls.
The friction from new grease is normal and does not impact performance and usually dissipates after a few hundred miles of use. YMMV.
Just my two cents.
Happy social distancing riding!