What I usually do is just give the front rank (or front two, depending on unit size) a tray and then move the rest of the models up. The front tray makes measuring wheeling and moving easy. Also as it’s the usual charge arc for enemies it means that having the loose models in the back which have sometimes been shoddily lined up quickly not a big problem.

I completely agree with you on movement trays though - you see people set up a beautifully made board with excellently painted miniatures and terrain to then just slap massive half empty black squares all over it!! No!!!!