Grew some last year. Dry spring until a wet june and beginning of July then no rain until the end of september. Test weight was light. They looked good through the dryness though. 13-1400 lb/A No fert but soil test N was high.
Didn't start combining until January but we had a wet fall. Last stuff I combined was a couple days after easter and getting down into the 6-7% moisture. Never had any fires or embers but I made sure to blow it off at the end of every day and change the cut direction to minimize the dust blowing back on the machine. The CaseIH spreaders seem made to throw dust up into the radiator. I would look hard at making a chimney to cover the screen for flowers. CR with a MAV doesn't seem to have that problem.
Converted a 1010 with pans and reel to fit the CR. Worked good. Would not want to be without the reel.
Got quite a bit done on the combine this winter since it was sitting in the heated shop the whole time, ha.
The whole process wasn't too traumatic. Put some more in this year.
We have a CR with standard chopper and only have to blow off engine once sometimes twice a day.
As far as sunflowers after canola, if I recall, our crop insurance wont even insure them if put on canola ground. I've never done or tried it but that tells me its not a good idea.
You want about 1lb of N for every 20lbs of yield goal. We shoot for 2000lbs here so 100lbs total N in the dirt at planting.
We generally don't put down any P since sunflowers do mine deep for nutrients, and we aren't set up all that well to apply before planting unless we use the air seeder. Even at our 2000lbs goal it's not uncommon to see 2400-2800lbs either.
You can solid seed sunflowers if you choose, but I dont recommend it. Many around us that solid seeded in the past have either hired or gone to 30" rows. I dont know your growing season length but we only seed around 21,000 population.
Try to combine around 12-14% moisture to keep the dust down. Any wetter and oil sunflowers get sticky and goo up the combine, but they can be takin wet. We've done some up to 18% in a bind.