I am painting on interior brick, already painted with oil-base commercial and wish to use commercial oil-base paint because I think it is more durable than artist's paints, i.e. dusted, perhaps even washed.

Is there something I can use to thicken it, thus allowing it to work more like artist's oil paints.

Thank you

Not with good results.

Some might suggest adding aluminum hydrate or magnesium carbonate, but I'm told they do not play well with typical interior oil based paint.

You are right to be concerned about durability. Artist's oil paint is basically just linseed oil and pigment, so you don't get the durability, finish or washability.

If texture is what you are looking for when you say "work like" artist's oil paints, you might consider using a good plaster, like Hydrocal. Give the current paint a good sanding, plaster the entire thing to the look that you want, then use a typical interior oil based paint on it.

Does that get any way near helping?