If you are stopped by police, you aren't required to converse with him. You need to hand over your license, vehicle registration and proof of insurance.
Wouldn't an appropriate answer to any "knock and talk" questions which is nothing more than an attempt to interview a subject "here is my license, registration and proof of insurance, officer. I don't believe we have anything to discuss" be sufficient?
I often drive around the country in an expensive RV. Sometimes the cops knock and talk. If you're foolish enough to willingly be engaged, it is your fault. I remember once I loaded up from my building I own there and ready to pull out of San Francisco but it was too late to drive so my wife and I decided to go to sleep there in a legal parking spot nearby with my then 5 week child in the vehicle. The cops came by for a knock and talk and asked me to invite them inside at about 2am in the morning. I laughed mightily and told them police or not, waking me up at 2am and asking to be invited inside wasn't polite, police or not and that I never invite police into my domicile or residence, which this motorcoach was at the time — and declined.
What could they do? Nothing. They left. I told them not to wake me up after 10pm ever again if they saw me parked around there, it wasn't appropriate and sent them packing. Never got visited by SFPD again, pulled out in the morning for my home in northern Nevada.
My father was a CHP officer for over 25 years so I'm familiar with cops. I don't hate or disrespect them, because of my familiarity with them i don't get intimidated by them but I'm also firm with them, too. I value all my rights and try to calmly and politely assert them when necessary and it has worked out for me for decades. I also do not hesitate to tell them I'm family when one tries to engage me, I assume that sometimes it could mean the difference between a hostile and neutral or hopefully positive encounter.
The only time I discuss guns with police in California is when I'm not carrying one!