the case law I am referring to states you must be very verbal about defending your rights, or you are considered to voluntarily be waiving them
There is a fairly recent case US Supreme Court case that I think addresses your question: Berghuis vs. Thompkins. It is somewhat complicated but, specifically pertaining to your privilege against self incrimination, if you are subjected to a custodial interogation, you must be provided your Miranda warnings prior to any questioning. This case, I believe, specifically said that a person needs to do more than sit silent - if that is all you do, the police can just keep questioning you. You need to assert that you are remaining silent and you need to assert your right to have an attorney present during any questioning in order to stop the questioning. You can't forever waive your right to remain silient, you can asset it any point during the questioning. I don't think you need to make a big verbal deal about it - you just say that you are not answering any questions and you want a lawyer.
The same can apply to consent as well. You might give consent to a search - and the police don't have to tell you that you have the right to decline giving them consent - but you can withdraw that consent at any time but you need to tell the LEO that you want them to stop the search.