As important as it is to get the correct mixture in your spray glue, even more important is to allow time for the glue to dissolve completely prior to spraying. I mention this as I once mixed the glue up in a clear bottle and was amazed at how long it took to actually dissolve fully. Most folks put it in a spray bottle shake a few times and start spraying. After that I now always premix the glue in a clear (soda) bottle and have been amazed at how much better the track has been racing.
our particular environment is a large facility with very tall ceiling and a extremely large overall space. When it is hot and humid, it is nearly impossible to get ideal track conditions inside that building so adjustment of the glue mixture makes up for that some.
I have never used anything but Camen brown and doubt I ever will. I spray differently for scale cars than wing cars and absolutely never apply any spary over a rubbered up track, i can't imaging that working very well. The track is always cleaned prior to spraying.
Track surface and bite also dictates how much you spray and where. A bitey tracks obviously needs much less in places than a slippery track.
I've used as little as 1/2 bottle of brown to a spray bottle to as much as 2 bottles of brown to a spray bottle depending on conditions and type of car.
We are able to run all classses of cars up to and including Open Wing cars on our track in spray glue and have turned more laps in spray with cleaner races than we ever had in racer applied glue.
There are "Racers" and there are "Talkers".....which one are you?