Nice incubator!
I used to use a plastic box with a 60 Watts lightbulb in it. Ooths go in there too in their own container. It worked well for P. paradoxa and P. virescens ootheca. Not I have bought a reptile egg incubator Lucky Reptile Herp Nursery II for my ooths. I wanted something fancy and with a stable temperature so I know for sure that my ootheca hatch the best they can.
For a heating method I would always go for a lamp, not for heatmats or heatcables etc.