Well, I think I can tell you what NOT to do... I had a similar problem, an imperial ale, US-05 yeast. My bucket got down to 55 the first night as a result of super cold outdoor temps. I warmed it on day two with an electric blanket over the course of the day. I got it up to 70 and turned off...
I have an imperial ale going in the bucket. The first night of fermentation it got very cold here (below zero) and my wort bucket was reading 55 (according to the Brewer's Friend Adhesive Thermometer. I wanted to get this up to the mid-60's so I wrapped it with an electric blanket and slowly...