I have been looking in many stores for blocks of smooth oil-primed paper but all I can find is paper with a texture similar to that of canvases, and it's not even as smooth as the smoothest premade canvases - it look subtle enough but the scans turn out all grainy. So my questions are:

1) Is there a brand which makes 100% smooth, oil-primed paper?

2) If not, is it possible to add further gesso on top of primed paper like you would do with wooden board in order to get a smoother surface or there are downsides?

3) Is it possible to prime ordinary watercolor/acrylics paper (say 300-350 grams) for oils with the ordinary water soluble gesso?

Thank you for any advice!