I have a painting that is quite large. It is polyester canvas (Feidrix brand I think?) stretched over very large and old stretcher bars that I had used in college but still in good shape. It stretched fine, put three coats of acrylic gesso on it and sanding in between. Then I used the normal neutral ground in oil. I started the portrait, but soon found that the surface is not very good. It kept dragging my brush. I tried sanding it down and I still didn't like it. I have probably half of the canvas covered in some sort of oil paint that has medium in it (Geneva mixed with Winsor and Newton). Is there any way to re-gesso it with oil based gesso? The fat over lean thing is what I'm most concerned about. I could probably use it as is as a landscape, but if there is any way to save it for the portrait, I want to do that first. Thoughts?