Josh, I assume you have touched bare metal at the high spots or close to it. When you begin your final blocking if you touch bare metal you will begin to build a lump since you will be sanding the low spots around it but will not be able to. bring down the high spots below the level of the bare metal. You can shoot extra build in the low areas but you had better shoot some all over if you have hit metal anywhere. Remember this is your final block and you want one consistent primer coat for you final color coat.