Thanks for your reply.
- Instead of buying a paper ticket, I buy the ticket with the oyster (i.e. the oyster serves as a travel card).
- As I understand, only customers with pay as you go oyster cards are required to touch in and out. If you have a travel card in your oyster, you are not required to touch in or out. This is my experience with the DLR, most of stations of which have no turnstiles. My oyster was inspected several times without me touching in or out, and it never posed a problem - as long you have a valid ticket in your oyster and you're not out of the zones in which it