I had battled with different cleaners for a while before I found that Simple Green degreaser was the most cost effective agent to safely clean glow fuel oil off of my aircraft no matter what they are covered with. I have used Simple Green on fabric, paint, Monokote and plastic canopies with no bad effects. I mix the Simple Green concentrate 1 part to 8 parts water and pour into a spray bottle. This mixture will cut through the oil and will not harm your finish as some ammonia based cleaners can. Simple Green cuts through the caster/synthetic oil effectively and it is environmentally safe.
The simple green can streak on glossy surfaces so I will use a non-ammonia glass cleaner to clean up streaks on canopies and glossy clear coats. Paper towels are wasteful, costly and not as efficient as using cotton hand towels. I buy bulk cotton hand towels (18-20 for $5.00 ) and wash them when they are used. The cotton towels absorb more and do not have the tendency to scratch glossy surfaces. To wash your washcloths, use the hot water setting and pour in a little bleach/detergent and you will get a lot of uses out of them.