I drove myself nuts trying to coat plates when we were putting the 'Silver Gelatin' book together. The best results I had with pouring on were when I preheated the glass, enabling the emulsion to stay hot & hence very mobile. A bit of dilution might also help, but you don't want to sacrifice density.

Apart from that I got very good results by totally immersing the glass in a bath of emulsion, then lifting & draining to one corner. The backs of the plates were protected with adhesive film that was subsequently peeled away.

NB, Aurum, the publishers have told me they are printing another 1000 copies of the book (no updated version though). Apologies for commercial break.