Without knowing more details of your current issue it is difficult to provide more accurate help, but you seem to be on the right track.
The D_SAMLAssertionDataPage provides you with all the data in the SAML response payload. If you can see the groups there it's a question of setting these in the operator. The challenge you may have is that you may need to provide logic in the Data Page you're using to determine which model operator to load based on the groups received. You could also use a data transform what would provide you more control over the groups and properties to set and you could also use the data page from there.
Do you have a specific error or something that it is not working for you?
Thank you both, the issue I had was trying to trace post activity and also the Data Page that sets the name of the Model Operator. I went and made all the changes in the post authentication activity to remove and add the access groups I needed and all worked.
Tracing the whole thing would have helped me a lot more but it worked.