When I visited the Musee d’Orsay in Paris, I often saw artists copying some of the masters' works. There is a program where you can sign up and request to do this on certain days in the museum. I heard the Orsay even provided the easels, and they have the ledgers from when the artists currently hanging in the Orsay signed in to do copy studies at the Louvre. This is one thing I regret not looking into and doing when I lived there.
When I returned home I took a portrait painting class in oils. The assignment was to do a study of apainting by John Singer Sargent. I was very excited to do this study of his painting Dorothy because I rarely paint portraits, this one would be a good exercise in painting whites, and an opportunity to really study Sargent’s brushwork. If you have never done a “copy” study, I would highly recommend it. Here is the link to Sargent’s Dorothy which is at the Dallas Museum of Art.