Bastien Lepage is someone I talk about frequently, and there's a good reason for that.
In my opinion, his unique blend of brushwork and form modeling is unparalleled. Take, for example, his iconic portrait of Sarah Bernhardt, which exhibits his masterful handling of paint and his willingness to leave certain choices unresolved or push them to a higher level of sensitivity.
For those looking for inspiration, I believe this painting is an excellent one to study. It's a very famous piece.