Cash is a tricky one. Generally I keep cash spends to a minimum. Any small cash withdrawls from my account are generally expense straight into Expenses:Cash Misc. and I don't bother tracking the inidividal cash payments.
However if it is a large cash amount (e.g. rent payment) then I will transfer from Asset:Bank to Asset:Cash before entering into Expenses:Rent.
I'm using CC for almost everything but there is still a lot that I miss because of random cash spendings.