When using my canoe (quiet water), I attach bow and stern painters to the carry handles. Any tips for keeping the painters ready for use when paddling, and stowed securely in the same place (without blowing around) when transporting the canoe on the roof of my car?
In other words, I want to leave the painters in the canoe, whether it’s on the water or traveling on my car.
PS I attach separate lines (not the painters) for my bow and stern tie-downs to the car.
I've never done it like you. Over many decades, I've almost always used my painters as my bow and stern tie-downs on my vehicle, which usually was a full-size van. That's easy, and can be done many ways. The photo below shows rear painter from grab loop to door hinge, wrapped several times. The front painter is attached to the front bumper with an S-hook.
More recently, when using a low sedan for car-topping, I use separate lines for the bow and stern tie-downs.
When I don't use my painters as my vehicle tie-downs, I most frequently just leave them loose on the floor of canoe for day trips, which makes them easy to reach and use, especially if the canoe went turtle in the water.
When I do this, or even if I
bungee the painters to the grab handles or decks, I will remove the painters for long distance driving, or tie them off to the other end's grab handles or thwarts, strung under the seat, for short drives. I realize you don't want to remove the painters for some reason, but it only takes a minute to do so.