This Concept Makes Playing Guard Easy - De La Riva Guard Control 

ankle grip can be stripped if you know how

If you’re doing Gi why not using the pant grip? One of the powerful grip imo with cross collar grip . Only down side is when the opponent goes to knee slide position you have to release the grips and go for rdlr cross collar sleeve on the other side but if you really know how to use those grip it’s nearly impossible to pass

Heel grip is easier to turn the leg like he mentions.