I think maybe you might want to use a combination of techniques here. First for a dense area of feathers/hair I think I would take and apply the feathers to a strip of fabric or perhaps sew them between two pieces of tissue paper so you have a line or string of fringe feathers. You can actually buy these feathers in this form. You glue that to the head where you want the dense hair and then on say the hair line at the front you would then punch in some individual feathers to make it look more natural. This is kind of the method that wig makers often take with wigs. the top, side and back of the wig is made up of machine made weaves of hair but then just in the front at the hair line they sew in a piece of hair lace (delicate netting) and then ventilate individual strands of hair in to make it look natural.
Another tip that may be useful when you want to insert and secure feathers. You punch your hole where you want the feather to be then you take the end of the feather and poke it either into the end of the glue gun or the end of a tube of glue. This coats the end of the feather in glue thinly and then you poke that into the hole. I do this a lot with full feathers but it is a bit trickier with the individual fronds like you are using. It can be done though.