The article describes if there is any order while performing the manual failover of redundancy group failover to other node.

There is no order while you perform the redundancy group failover, however be vigilant while you perform the RG0 failover.

A redundancy group 0 failover implies a Routing Engine (RE) failover, in which case all processes running on the primary node are killed and then spawned on the new primary Routing Engine (RE). This failover could result in loss of state, such as routing state, and degrade performance by introducing system churn.

Hence a downtime is required while performing RG0 failover.