Yup, it uses air blowing out, I think the regulator is set in the 3-15psi range, with a very fine line between too low psi and the plastic just melts away (air gets too hot) and too high and the plastic gets a blast of warm air.
The key is to have the hot air soften the part to where it is flexible but not yet melting, and the filler rod to be just warmer than melting. That way when you push the filler rod into the piece it just melts its way in.
Literally it took me 5 minutes of practice to get confident enough to work on a bike. The learning curve is almost non existant
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