I used a cheap hot air soldering station for three packrafts (Telkwa, 2P and UL). I think you will find it with different names, but it’s always something with “858D”. I bought this: https://www.amazon.de/Digital-Desoldering-Reparatur-Werkzeug-Elektrowerkzeuge/dp/B074N1FR9N
I dialed it to 270 °C and intensity of 3.5 for the normal Telkwa/Skeena-Fabric, and to 300 °C and 1.0 for the UL fabric. That worked like a charm. The seams are very consistent and clean and, if you are careful, without any air bubbles.
I used it for all of the seams and for difficult corners. For other parts (like soldering the main pieces to the floor) I used the leather iron. In those areas, the iron is a little bit faster.
If you have more questions, don’t hesitate to ask.
Christian