"There is no such thing as bad weather; only bad clothing."
Aside from layers and high calories and hot beverages, (oh my!), on alcohol and propane stoves, I like to invert a terracotta flower pot over a burner, that can then be held on with fiddles.
An old salt once told me that by dipping the pot in seawater, I'd get a more humid heat, I've yet to try that, but I do like to spread the heat around with a small battery powered fan. I keep the flower pot in tupperware labeled "amplified heat".
There are the disposable hand, toe, etc. warmers, as well as the more permanent hand warmers using fuel sticks, you might look at?
We also occasionally use a small Coleman catalytic heater that runs on propane. I close off the aft and forward cabins to just heat the main cabin and head.
Much much easier to stay warm, than to get warm.
The Sea is my Church; the Boat is my Pew.