Thinning Oil Paint?

I notice alot of figures done in oils have nice smooth surfaces after painting, but mine on my first figure was very rough. I think I didnt thin the oil paint enough, I used Liquin to thin it. Was this the right thing to use and also how thin should oils be? Could the problem also be to much paint? Any help would be appreciated, my figure is on the figures forum if you want to see the problem.