Not Heated Build Plate Glue Amount and Dry Duration
As a fellow Flux Delta owner, I can answer this question with certainty. Two layers is sufficient. Be sure to consider the size of the model being printed and the additional area covered if you are using skirts or rafts.

If you apply the glue stick at the moment you turn on the printer, it will be dry enough to work properly. The printer "uses time" to initialize and to calibrate which provides enough drying time. You will also "use time" to load the software and import the model.

It is not necessary to remove the glue from the plate after a print. For succeeding model printing, ensure that you've filled in the areas missing glue from removing the previous model.

You will want to remove the glue (hot water works good, but the build plate gets hot!) when you feel that the glue build-up changes the texture of the bottom layers.

You may have already learned from the forums that you print on the non-grid side of the build plate.