The first time I worked on synthetic paper (yupo) with illustration colors - I swore I would never do it again. The paint was extremely delicate, and even just the lightest brush over the surface would leave a scratch...
I have since done many, many paintings on synthetic paper(s), and continue to do so using Illustration colors. What I found was that after some time, (a few days, to a few weeks) the paint actually gets much tougher on the surface as it continues to cure. I do wipe the surface lightly with windex or a mild, soapy solution of warm water, simply to assure I have not left any finger prints on the surface prior to painting, but that is it.
I have found that any additional prep basically undoes the reason you would use a synthetic substrate to begin with. Same with adding bonding agents, like 4030, and the like - if you are going to undo the ability to manipulate the paint on the surface after application, then it is simply better to choose a more suitable substrate to start with. There is a learning curve to working on this stuff, but it pays off in the end.