You are right on spot with putting a foundation less frame in. The bees will draw what they want, in this case their priority will be drone comb. I suggest two foundation less frames per brood box. Put them at the edges of the brood nest but not the outter most frame, so positions 2 and 8 in a ten frame box.
When they have all the brood comb they want, they will draw the rest as normal cells. The also love to fill drone comb with honey when they don't need drone brood.
My hives are completely converted to foundation less. I like the results. Just pulled some beautiful cut comb honey this morning.