i have done a number things frank, but again let what i say be only a guide for you. we had and have had poor nectar flows for the past couple years. feeding is necessary to build them up if need be and also to sustain if required.
i have started pollen subs much earlier to enhance the buildup to divide before the dandelion flow, so that i have strong divides for the flow. what this does though, it takes away from the strong colony/s that might make you 2 to 3 times the honey that the divides do for that flow. so sometimes, with very strong colonies i will not divide them until after this flow is over or only do a 'soft' divide. as far as swarming with this, i keep them busy building comb in supers or in the deep, making sure there is plenty of space for the queen to lay and they are not getting crowded. you can keep feed on, syrup pails, until that comb is built. do not use a queen excluder at this time. remove the syrup when the flow starts. have to keep an eye on the comb building with syrup pails on overtop supers, you don't want syrup in your honey supers, so a matter of timing and a close watch. the soft divide is to remove just enough frames and replace with drawn comb/foundation. if the queen lays up in the super, not a problem, just move her down to the deeps, place the excluder on and the bees will take care of the brood. when that brood hatches, the bees will clean and polish the cells for the liquid gold.