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Prioritization, on CBWFQ output policies, is done by using the priority or bandwidth statements. The former places class traffic into a single queue which is always dequeued first, the latter places traffic into a class queue with dequeuing priority relative to other class queues. (Class fair queue creates hashed flow queues. Pre HQF, each of those queues competes with other class queues and relative priority is also influenced by IP Precedence, post HQF, each queue competes within the class priority, equally.)
BTW, except for pre-HQF, IP Precedence (or ToS byte), doesn't really matter. ToS's purpose is just an efficient way to examine a packet for QoS classification, i.e. it's not required to accomplish traffic prioritization.
PS:
Unless you really understand QoS, and different traffic service requirements, I would suggest you avoid trying any explicit priorization scheme. Instead, I suggest you just try using a policy with class-default using fair-queue. (NB: If the next path's bandwidth is less than the interface's, use a two level policy. Shape in the parent, and class-default FQ in the child.)
