Here is a list of some books that I found helpful to learn how to paint in oils. Some of these are still in print, but many are not. You can look on addall.com or bookfinder.com for the out-of-print ones.
Methods and Materials of Painting of the Great Schools and Masters, Sir Charles Lock Eastlake, vols 1 & 2
Oil Painting Techniques and Materials, Harold Speed
The Materials of the Artist, Max Doerner
Technical Drawing, Giesecke, Mitchell, Spencer, Hill
The Materials and Techniques of Painting, Jonathan Stephenson
The Painter’s Methods and Materials, A.P Laurie
Perspective for Artists, Rex Vicat Cole
The Techniques of Oil Painting, Frederic Taubes
The Artist’s Handbook of Materials and Techniques, Ralph Meyer
Linda Mann Artist 