I think Newell mentioned using oil with resin in changing proportions but I could very well be wrong. The book "Gunsmithing" did mention using oil with resin and as I recall increasing the proportion of oil in the later coats. "Gunsmithing" was a reprint of articles published by Wolfe, the book is out on loan so I can't check. I'll check Newell's book.

The key elements in human thinking are not numbers but labels of fuzzy sets. -- L. Zadeh

Which explains a lot.