Any of the cleaners that the fabric mfrs. suggest for "safe" cleaning that I've used don't get tough grease out. I've had success in the past on lycra, nylons and other synthetics by using waterless hand soap such as found in auto parts stores. Cuts grease really well. Don't get the type with added gritty pumice, Take a Q-Tip and rub it on the grease spots and let sit for at least an hour. Use cold water to rinse and repeat if necessary. I can't guarantee it won't harm the waterproofing but I haven't found anything else that will get the grease out as well as protect the WP coatings. You can always apply new waterproofing if it gets damaged.