I took a look at a couple of tiles I prepared last evening… decided they need a 2nd coat of my mix. I may be over-brushing in an effort to minimize brush strokes… 
Interestingly, Ron Clarke, just this morning in his LightBurn thread, posted his current “brush on” recipe…
Here is [Ron’s] method For best results with a brush on method measure out 100 ml of PVA glue and I now add 3 tablespoons of water plus two drops of liquid hand soap. Mix thoroughly. Now add one full tablespoon of titanium dioxide to a flour sift. Slowly mix sifted powered to your PVA as you stir. Make sure you mix well. I now strain this mixture through the flour sift into another vessel. Paint on clean tile as you would paint anything with gloss paint. I dry with hairdryer and laser at 1000 mm/m 80% power. 40 watt diode laser. Hope that helps. Substitute hand soap if necessary for washing up liquid.
Ron’s recipe is just the three main ingredients for water-based paint – glue, water, and TiO2 powder – but is far more glue-heavy than any other recipe I’ve seen. No additives other than a couple of “drops” of liquid hand soap.
I’ve thrown out all my previous mixes – except my latest – and have mixed up Ron’s concoction as well. I didn’t have the sifter so just spent more time stirring the mix as I went. He also uses a hair-dryer to speed up the drying process. His speed/power settings are not far off mine for my little 2.3W Banggood laser as well. I’ll test both concoctions to see what I can see.
— David