I always used a heat gun and man sometime I fell like I'm gonna burn a hole through that hull!!
The nice part about using a halogen lamp is temperature control, moving the lamp closer or further away to slowly achieve the desired temperature over a large area, without standing around waving a heat gun, trying not to rush things and see bubbling plastic. S L O W L Y, so the hull material heats all the way through to the inside.
I use the Almost An Ouchie That is Hot test, when I can still lay my ungloved hand on the hull for a second or two before saying ouch that is about as hot as I want the plastic.
I have one of those single lamps as in your heated hole, and a duplex halogen flood on an adjustable height tripod stand. That latter one is great, I can adjust it to the perfect hull height and aim both lamps at the problem area.
The first hull I ever fixed that way still seems miraculous. A friend said he had dented the nose of his Dancer kayak. Sure, bring it up and we can do something.
It was the weirdest
dent I have ever seen. He had pitoned a rock. The bow of the Dancer was no longer an outie vee, it was now actually an innie vee.
We pondered for a bit and made a bow shaped plug from rags and wood, attached to the end of a brookstick. Heated the bow with the halogen lights and when it was warm enough pushed the innie vee back out into an outie.
It was not perfect, but it was danged close, and easier than I thought it would be.