How do I reuse an artist oil paint canvas, what is the best way to prep it?

Is it already stretched? If not, restretch it. Is the old paint really built up on the canvas? If so (assuming it's prestretched) you might want to undo it and stretch it again, which can flatten it out. Then you gesso it. I would suggest two layers of gesso if you don't want the old stuff showing through, but if you like the old layers, just start painting. If you're painting in oils as well, you'll have no problems (I wouldn't recomed putting acrylic on top of an old oil painting though). Starving artists have been painting over old canvases for hundreds of years.How do I reuse an artist oil paint canvas, what is the best way to prep it?
Just what the last person said, you may also scrape off some of the old layers if they are too thick, be careful and don't damage the canvas itself.How do I reuse an artist oil paint canvas, what is the best way to prep it?
you can do what the first person said. if it is an oil painting you can prime it with an oil primer, but this takes a while to dry. also, it is good to cover the canvas with a solid color, before you begin to paint over the painting. a gray would work, white and the cadmium's take a while to dry. my instructors always advised for us to do this.
If it is painted with acrylic paint you can paint over it with white paint. If it's painted with oil paints, you'll have to take it off the stretcher bars and restrech new canvas. If you don't need it to last more than 20 years, you can paint over it regardless.