Another approach is to apply fixative. This is a thin clear film sprayed on over the sketch. Fixative is obtainable in spray can format at art supply stores. It is used as a final protective coat over charcoal and pastel drawings, but it can also be used to protect preparatory sketches from smudging when painted over in oils.

Artassist,
As Don stated, Re: turped-up paint, it means,
“paint thinned with a bit of turp” (or OMS).
Just thin the paint out so it really bights into the
paint-surface (and dries faster, too). There, one
frequently employs a fast drying, popular under-
painting color, such as one of the umbers, as
they’re the fastest drying paint anyway.
On top of that, though, now, they’re thinned-out,
too, which only makes ’em dry that much more
quickly.
r

Last I sketched on a canvas, I used a charcoal pencil, then erased almost all of it with a kneaded eraser. What was left, did not smudge with the paints, even when I used very light yellow/white paints into the edge. :thumbsup:

I would like to sketch my drawing in pencil and paint directly over with oil paint (Winsor Newton) however I am concerned that the pencil will smudge. I also have pastel pencils. Would these work better?

Pencil will smudge and become integral with the paint. I have been using pencil for 40 years or so without a problem and all I do is draw lightly which minimizes or eliminates any smudging.
Because I work in layers, it will be covered up anyway.
I don’t know about pastel pencils as I have never used them.
I wouldn’t use fixative as suggested as it adds a complicating layer to the paint film, especially hair spray as I have read that this isn’t good even for fixing drawings on paper.

I also would like to paint directly onto the canvas with the oil paint, without really using linseed oil or distilled turpentine with the paint. Can this be done?

Yes, and it will usually form the strongest paint film. The only reason to add oil or solvent is to modify the way the paint handles, usually making it less viscous so it is easier to push around.

Should I underpaint? Is it necessary?

No it isn’t necessary. Alla prima painters often paint in one session. Some paint on a pre-toned canvas, or even put a thin wash on the canvas first.
My problem with only using one layer of paint is the transparency of it, but I paint very thinly.

fix it with spray fixative, it works very good.

So is everybody pooh-poohing that business of pencil “migrating” up through the paint? Some of my reading says that graphite is a no-no, but I’d love to learn otherwise.