I too just bought a Dyna Glo large off set smoker and seasoned it Monday of this week (2/22/21).
If you fill up the charcoal box/off set fuel box, to the top and use a roofing torch to light it, then you will reach a temperature of 250 degrees. Keeping the charcoal box full will give you a more even heat for a longer time. I also sealed all of the seams with Lavalock RTV450 Black Silicone Sealant. I also installed Fireblack Hi Temp BBQ Gasket High Heat 1/2 x 1/8 gasket around the inside edge of the firebox. Any where you see smoke coming out get some chalk and mark the spot then come back when the smoker is cool and place the silicone to seal.