A lot of people probably know the benefits of deadheading sunflowers, but I didn't. I've been deadheading one of my sunflower patches- one with a a lot of multibranch varieties in particular, and I have experienced nice results.
I planned on just letting nature run its course when I planted this patch, but the birds never found the spent blooms like I had hoped. (Which was disappointing, because I was going to wear dorky bird watching attire and lay in the front yard with a camera and binoculars to freak my neighbors out... oh well). I suppose there are just too many feral cats in the front area. Anyhow, my plants were looking sad, so I decided to dead head and also remove the scraggly leaves that seem to build up from insect damage and shade.
What's fun is that I have found that the plants have become much more productive and the blooming season has just continued on without pause. Some of the stems I have snipped have developed 3-5 more flowers. They have been a little smaller than the original, but still very showy and the color has been a bit more vibrant. I also have plenty of seeds I've harvested and saved for next year- though I read somewhere that they "wouldn't be any good" if not already dried on the plant, but I think I'm going to take my chances. You do have to let the deadhead remain on the plant for awhile for the seeds to form, but they seem to be ok after that.
Now, I suffered a bee sting , 2 ant bites and I almost fell off a chair today- so if your not willing to risk injury- forget about it. But, a neat thing I've read is that you can also do this with the non-multibranch varieties as well. Just like the multibranch, it is supposed to encourage small blooms from the leaf joint areas and extend you enjoyment of the plants, or it will direct energy to small buds already formed on the plant and help them reach their potential as some none multibranch will still produce several buds ( I have a mammoth that has extra buds on it right now.)
When you deadhead- look a few inches down the stem from the flower. You will see a leaf or two... or a leaf joint area. This is where the next bud forms. You snip above that.