With this handy little tool you can clean your carbon rods even when the lid of your bambulab printer is closed.
Just put Isopropyl alcohol on the sponges, snap it to your carbon rod and move it back and forth a few times till they are shiny again.
For the sponges you can use a normal kitchen sponge (be careful to not use the abrasive ones). Cut two pieces roughly about 10x20x20mm and press them into the spongeholder.
For the pullback mechanism you can either print the provided spring in TPU, or use small hair rubberbands. The spring also works in PETG but looses its strength from time to time.
More info about cleaning the carbon rods can be found in the Bambulab Wiki