Today, a friend and I got out supplies and tried every medium we had tucked away around the houses. Finally found one that is soft and doesn't bleed: Golden soft gel medium, matt. For a water color look in the background, Textile Medium, GAC 900 works well. Got a little more done on the lily and will post pictures when you can tell what it is.

I've been using Golden Fluid Matte Medium with good results, too. Soft and no bleed. I haven't tried my Liquitex Matte Gel Medium yet, but may just for fun. I suspect it's too thick. The GAC 900 releases formaldehyde when heat set, so I stayed away from that one.

Looking forward to your posted results. :)