I haven't done an oil print (yet) but I do now a little bit about paint that might help.
The difference between the different oil based inks/paints is usually the binder they are mixed with. I've heard that you can use oil paint, but it is a very different constancy from a litho or intaglio ink. You could try adding sun thickened or polymerized linseed oil to artists grade oil paint if you absolutely can not find a litho or oil based etching ink. Also litho inks often have resins and waxes to further their water resistant properties.
Also litho inks (tend to) use pigment which will not be soluble in water. Oil paint isn't expected to get wet, so research into specify pigments is needed. Another thing to avoid is 'water soluble oils' sounds obvious, but they would desolve in water.
In printmaking classes we would often take a xerox copy, saturate it with gum arabic, then ink it up with oil based intaglio inks just like an oil print is done. So I wouldn't worry too much about using an intaglio ink in place of litho.
Anyways, that's my 2 cents, hope it was helpful.
Thanks alex, it does help. I'm curious about this xerox print method...
Glad I could help. The xerox is super easy to do, the only downside is it can only reproduce solid tones and not gradations. I never tried using a photocopy of a halftone, so that could be an option.
Your going to need a decent amount of gum arabic. The quality of the gum arabic isn't so important, and I would definitely not be using anything that looks like this . Its a much higher end gum arabic than you need, get the cheaper printmaking grade if possible. Also you need an oil based ink (or paint if your thicken it)
First thing it to make a xerox (toner based copy) of whatever you want to print. Place it copy side up on a glass surface. You want to saturate the xerox copy with the gum and rub it in gently. It should look soaked. Then you spritz the copy with tap water. Prepare your ink by warming it up, then preparing a even coating onto your glass pallet and roller.
Once you've got your roller evenly inked, you will roll it across your xerox 'plate' once. Then very, very softly roll it across a paper towel to remove any water on it. This is to prevent contaminating your ink. Re-ink and roll across a new segment of your xerox, roll along a paper towel, ect. Once you've inked in one direction, turn the 'plate' 90 degrees and ink across your previous marks. You may have to lightly spritz your 'plate' with water during the inking process.
Once you are sure you have an even coating of ink, you carefully lift the 'plate' up and put it ink side down onto whatever your receiving surface is. We would use a press which is set to put a lot of pressure (similar to intaglio prints, or litho). But if your careful and take your time you should be able to use a large spoon and burnish the image into good contact. Depending on how fragile the plate is, you might want to put a medium weight printmaking paper between the spoon and the xerox plate. I'm thinking like a rives bfk, or stonehenge (both which would be a great paper to receive the print from the plate). Its ok to lift a corner to see where you've missed, as long as the rest plate doesn't move.
This plate should be durable enough to yield a few prints, but the key is to keep it wet by spiriting it just prior to putting a new coat of ink.
I'd be happy to answer any more questions about this. We would usually use this for putting a pre-made pattern on linoleum, or perhaps as a temporary etching resist. Its not really a medium in its own right due to the relative fragility of the plate and short lifespan. That said, its still wiked cool and a useful tool