New, trouble shooting with odors

Hi everyone,
I have been WO for about a month and a half now. I don’t know if I do it right but I really don’t like the smell of my hair and I don’t know what to do. I wash my brush, the bb smell like a bb I think but this is not the same odor. Also, build up is forming pretty fast on one place of my scalp, just behind the center of the head. Other places are just fine. No dandruff, no itching. I wash my hair with hot water and a comb twice a week and rince with cold water. I only rince with cold water other times if I want to work my hair. I have long dark hair, very thin. When using the bb on dry air, I have a LOT of static, so I’m not using it often.
Can you help me?