This is a link to an interview with my great friend and artist Robert Senior, which gives a deep insight into how he works.
https://www.jacksonsart.com/blog/2022/11/27/robert-senior-oil-painting/?fbclid=IwAR0o9Aa9nVK_XPJbczrM8PcpXLIMic0XBA1zS_3g7mlidOPDnqlPLEcue8Q