Hi,
I use the Polaroid sheet polarizing film on both of my 30x180 softboxes, for 2 by 2 meters artworks a smaller softbox will be adequate. I use strobes.
The cross polarization will work and it will kill virtually all reflections from the painting. I would have preferred to check how the your lighting works for your particular artwork, it might make the painting look totally wrong /dull if you kill off the specular reflections.
Usually I like to shoot several shots with different levels of polarization, and several exposures without any cross polarization and work / mix them in post production to make the image look right. Sometimes I also add an exposure, shot with only one light at an oblique angle to expose the structure of paint on the picture.
If you decide to keep some of your specular reflections, your white canvas can be used to place it in front of your artwork and shoot through it. It’s how we shoot the Orthodox icons and metallic acrylic paints.
There is no rules, as far as I know. An available light is very nice for copying work and you can make a White Shading shot / LCC shot to make the light from the window even.