[Rusty's Momma]

Rusty's hair does this spikey, clumped together thing that I do not know how to fix. I can brush it with a slicker and when I am done Rusty will shake and POOF instant spikey, clumped toether hair again. Does anyone know what causes this or what I can do to take care of it.
I have considered having him trimmed, shaved, whatever but he is 9 months old & I have NEVER even had him trimmed. His hair grows sooooooo slow that I am afraid to do it not knowing if it will NOT grow back.
????????? Any suggestions here??????????