It is a learning curve with them. I think spraying water is pretty much a must for better absorption and more even watering. I always hit the outer part first, pretty hard and do the same for all the pots and have a little soak period. The next rounds start with the sides and fill in the center. Usually three rounds of top watering is good and I leave a little to water in the tray.......using muscle memory for the weight.
If using chemical nutes, just do the same with all top watering and using muscle memory for the weight to tell you when to stop.
I think a surfactant is a must with Rain Science bags to help prevent dry pockets, mainly on the outside. I got the ThermX70 that Jeremy of BAS was using in his first 10x10 series and he switches to 'The Q', Quillaja extract in the next. No idea if it's better, but with either one, a little goes a long way. The ThermX70 works well and it's a VERY dense product. I put some in a much smaller bottle, but a better option would be a bottle used for dispensing ketchup with a nozzle and small cap. I still have enough for at least another year. I'm only on my second small bottle.
I use it in all my water, except for normal rez water. I do add it to the first couple of small rez waterings and with anything sprayed on top.