This is the most difficult task we face. Usually I keep a .27 nm velocity loop running almost continuously watching for microbursts and larger scale outflows.
Theory says to look for mid-level convergence at or just below cloud base.
This indicates when the microburst is about to occur. Also, lead time is still only a few minutes. If cells are isolated, I do run four-panel and watch for descending reflectivity. Both would give about the same amount of lead time. Don't forget fire weather.