I have put on tips on existing limbs using a large cardboard box and a worklight. Got up to 140F and sometimes higher. I was worried about the box catching flame, but it has to get to 230F I believe. If you regulate the temp to under 150F, it can be done.
If I was going to go thru all that trouble, I would just build one for less than 30 dollars. I got my plywood from a giveaway on craigslist. Only thing that cost me was the foil insulation.