Gas vapor is very flammable and could cause an explosion in case of any spark. Diesel is quite different and not as flammable. what I have done in the past was to take a long piece (30" long or a bit longer) 1/4" all thread and welded on a brass circular metal brush (from HF). You can dump most of the fuel in a bucket from the stop valve at the bottom of the tank. I mounted the rod to a drill and slowly brushed off the bottom and side of the tank. I did have the tank out but i don't think it is necessary, i then sloshed the diesel around and dumped the fuel in to a cup and it had some sediment and stuff in it. I actually filtered that fuel and put it back in the tank. Did it a few times, filled the tank and used the tractor for a few hrs and then changed the paper filter media in the bowl assembly.
Jc,