I use a small butane torch to melt drops of crayon on to the canvas, placing the color blotches where I want them. Then, either I use the torch to move the color around as I rotate the canvas, or I melt the blotches, cover in wax paper, move around with a small travel iron.
Perhaps the poor artist’s encaustic.
(Yes, Crayola brand crayons work best, and some things they call “crayons” are actually plastic! And people are overjoyed to give away their old crayons.)
Click here to go to the archived site which is a pretty extensive catalog of most every piece I’ve made from 2009 to 2016, some of which include stories about how the art happened.