Reapply vulnerability item assignment rules and vulnerability group rules

[Feddy]

Hi All, 
We have a requirement where we need to reapply vulnerability assignment group rules since cmdb records are changing continuously. I noticed that if we activate  OOTB scheduled job "Reapply all vulnerability assignment rules" (in inactive state by default), it really run all the rules on open VIT . My Question here is can we include only specific rule to run in the job? Alos it does update the group correctly but it didnot delete vulnerability group .I need to reapply the vulnerability group rule manually. 

Please give your inputs on , 
 1. How to reapply specific vulnerability assignment group rule (it runs all the rule in OOTB)
 2. How to automate reapply of vulnerability group rule? ( I need to do it manually by opening individual vul group rule and click reapply action)
3. What else needs to be considered when we activate the scheduled job? 

Thanks in Advance

[Feddy]

can you please let me know how to reapply all the vulnerable group rules?
I need to reapply all the vulnerability group rules at once or can you suggest some custom approch?
instead of deleting and recreating the groups, how can we add the vul item to respective vul group?

[AndrewP]

How do we get to AssignmentUtils to enable reapply of all? "The configuration for the job Reapply assignment rules (VIT) is inactive. Please activate to execute this background job."