Hallo Kairi,

At first you must let smoke away all the oil. Hold the painted workpiece near the open an hot kiln until the oil begin to smoke. Take the piece away and wait, until the smoke is gone. Make this step several times, until nearly all oil is evaporated.
Now put the piece into the hot kiln. Observe the piece well. As soon as the rest-oil start to burn, remove the piece from the kiln. Let the oil burn down. Make this step again, if the oil is complete burned. If the oil realy is burned away, put the piece in the kiln and fire until the enamel surfaces is smooth and shiny.
In a second firing you can fire a thin shift of very clear flux over the painting.

Never  apply a shift of enamel over an oil-painting, before the oil is fired away.

Edmund

Hi Kairi,
One more tip. Have you ever tried the Acrylenamels of Thompson? These painting-colors are much more easily to process than oil-based enamels.
If you want more info, you can ask me per email.
These pieces were painted with acrylic enamel.

Edmund

Yes, i have acrylic enamels too, i thought before to try taditional technique as we learn in the school, but after i tried acrylic, i found acryls more convenient.

i got pretty nice result, with minor unevenness and contours have more luster, i affraid to improve, but dont want  keep it too. So i think, maybe i must varnish all my work, or does exist  clear enamels, for getting smooth transparent surface? Which one i must to choose and how to use?

Hi Kairi, 
It is not nescessary an overlay-shift of flux over an Acrylic-enamel painting to apply. Acrylic Enamel contains glass formers, so the painting flows out smooth and shiny. If painting is too pasty or to relief-like, you can dilute the Acryl-painting-colors before painting. 
If you want an overlay of flux to apply, I recommend one of the soft Thompson enamel Fluxes. Which is suitable for you best, you have to try.

Edmund

Hi,  i took copper plate, i enamelled it with white thompson enamel - pretty nice.

Then i mixed painting enamel powder with sandalwood oil and covered pre-enameled surface. I put it into the kiln, a small nice explosion occured, my work was burned.

I took it out of kiln, my work was sooty, i washed soot away, but result was litlle but dirty and paintig was partially cracked.

Next time i let new test dry 24 h, but almost same result with smaller fire, explosion. Soot was same heavy, but overwhelming washable.

Now i would like to make small Picasso painting on pre-enamelled silver.

What i do wrong?