Wait Time for NVC letter after 130 approval

My parents 130 application was approved and approval notice sent to NVC on Oct 31 st, 2018.
1. How much time does it take for case assignment for CP in new delhi
2.regarding designating an agent , should i keep myself as agent ( does it cause delay )or pick up an agent in india , can my parents be their own agent , if they correspond by email , i prefer being the agent myself to better coordinate
3.any steps that are time consuming that i can take while waiting for better the case assigned
4. which form do i use for affidavit of support ( both parents had separate 130 application approved)
If there any one in the forum who has gone through CP from india , who can guide , will really appreciate