I'd love to know how it turns out. I feel like the general rule is you don't want the beer to cool more than 1 degree per hour or else the yeast might begin to go dormant and floc out.
Personally, I would have just let it keep rising from that first time you got it to 64. The first couple days are the most important for temp control, and especially since you're gonna want some decent attenuation on that beer, letting it rise to 70-72 in the later stages of fermentation is not a bad thing. It will encourage the yeasties to really max out the ferm.