nope no need to flush at all if you're ppm's are moderate. If you would like, you can flush with 1/4 nute strength once a week.
small pots would need watering more depending on the size of plants and how much light/heat your plant is getting. Again no runoff if using moderate ppm's.
And whatever coco you get, just make sure you flush out all the excess salts before using it. (really really good flush)
What ppm's would you consider moderate for bloom stage? I'm thinking of doing this. I use a ph meter with .5 calibration. 2 and 3 gallon pots. In veg with runoff, my girls liked 750 ppm's. In bloom with runoff, they got fert burn at 950 ppm's.