I have the exact same Planar 2d portable heater. When I’m making breakfast, I usually just run the heater on the highest setting for about 10-15 minutes with the hose laying on the ground, not routed into the tent. Sometimes I put the end of the hose into the reflectix bag I made for my water jug for winter camping, while it’s on max. see link below
I have cold weather sleeping gear, so I don’t run my heater all night. The Planar 2d gets the GFC way too hot for my taste, even on the lowest setting. If it’s mid 20’s F outside, and I’m protected from the wind, the Planar on low can get the GFC tent close to 80F. So usually, I just run it for about 30 minutes before bed, and another 30 minutes in the morning so it’s way more pleasant to change clothes and get into or out of bed. When it’s super cold and/or windy, I’ll run it all night then of course.
The kerosene is a good suggestion too, but I think running it on max heat for about 10-15 minutes periodically will do a lot to burn all the soot off.