What products do you use to clean a canvas top?

Only use automotive non-detergent shampoo that have no oils. Something like Wolfstein's RaggTopp Cleaner. Use a soft scrub brush instead of a hand mit as the mit (or cloth) will probably leave lint.

Wet the top, apply the soap and clean with the scrub brush. Use lots of water and then dry with something like a synthetic chamois or microfiber towel.