The initial test on a six inch piece of test track of powdered glue as ballast adhesive showed promise.  I’ve since moved to using it full force on a large N scale project in my shop.  Again, success.  I find it is not only easier to use than traditional liquid adhesive but it’s also easier to get better results.  Better being defined as no floating ballast, no craters, and no mini trenches.  I haven’t yet dialed in the best ratio of glue to ballast so can only say the amount of powdered glue needed is “not much”.  At present I’m putting two, 10 oz. bags of ballast in a bucket with only 1.5 oz of glue and it holds very well (that comes to 1:13).  One caveat is that the glue is very sensitive to moisture in the air and when exposed to it will start to dry.  I’m noticing that after mixing the ballast and glue in a bucket and leaving it over night there was some drying.  That being the case I suggest storing your excess in a container with an airtight lid.  If over time I find I didn’t use quite enough powder the ballast would be knit together enough that a quick follow up with dilute matte medium would be easy to do as insurance.  Finally, there is warning label on the glue container letting you know the powder is a lung irritant and not good to breath.  That is certainly the case so wear your respirator when working with the stuff.