Thank you so much, Anthony!! I appreciate all your kind explanation…you have helped me a lot clearing my doubts. I agree with what you´re saying, oiling out or working into a couche should be used if its absolutely necessary not imitate so and so artists. If one is not careful is very easy to add too much oil and have a very glossy slippery surface. I have had one experience with a painting that whatever I was doing to darken a color…it seemed that anytime that it dried it always seemed to remain the same value as I had it before…in that case it was very important for me to oil out the painting…and as you have kindly mentioned that could have been of me not using the right medium(too much solvent too little oil). In another occasion I made the mistake of oiling out only the cast shadow area of the subject on the wall…when I oiled it out it already look dark and made it even darker when I finished painting it. I would love to fix that, but I might have already added too much oil when I oiled it out that it might not be a good idea.
Here´s a piece where I had to sweat working with a slippery surface after oiling it out:
