I start with the face. regardless of the painting -- if there's a figure in it, that's what I tackle first. for this one though, something different.
my usual process: I will get my lines down in pencil, then with very little planning or underpainting, settle in for what generally amounts to be a very long night. I've always painted this way, when the paint is wet. it's a sort of alla prima I guess. and while I will eventually go back in and add some glazing and detail work, for the most part, that first session is also the last session.
There are advantages to starting a piece this way for me. the most obvious of which is that the paint is wet that first day; the entire face can be worked and refined at the same time, making it easy to keep a uniform feel. I don't have to worry about going back into already dry paint if I knock it out in one sitting, and despite the years I've been at it, there's something I find intimidating about starting a painting. faces are a definable area; it's easy to paint up to a hairline, and a jaw line, and not worry that the transition to the next body part will look off. I think I initially started working this way as a sort of backup/escape plan -- i.e. if the face looks funky after that first day, the painting might not be worth finishing. so I'm sure these habits were born of a lack of confidence, as much as they are tricks and "shortcuts".
plus there's element of torture and endurance in there -- and I'm all for that.
speaking of torture, the downside of this method, is that I need a good 8-12 hours to paint a face...at least (and contrary to my expectations, I'm definitely not getting any faster). I do like painting for super long sessions, but it's a drag to not have other options when I need them. painting that long is super exhausting, even with my cushy floor mat and snacks. generally after 14 hours, if my eyes aren't totally shot, the paint starts to dry anyway.
SO, I decided the approach this one differently. I did a sketch, tinted the panel and bit, and started with the eyes. I didn't think about any other area of the painting, and actually didn't think much about how I was painting. When the eyes were done, I stopped. novel!
Oil paints get slightly darker when they dry, which is one of the reasons going into already dry paint and trying to match colors is so hard. things look right, then the paint drys, and everything is terrible. one way to get around this, and make the dry paint easier to work with, is to add a light layer of medium to the dry paint layer before you put any actual paint down. supposedly this is called a "wet cushion" (which they may or may not teach you on day 2 of art school, but it took me years to figure out). it also serves to "oil out" the dry colors and bring their vibrance back -- which is especially helpful for darker colors. I've been using Oleogel as my primary medium for a few years now, and it works great for this. Oleogel is a soft gel that doesn't speed drying noticeably, and isn't sticky. think of a much softer vaseline. it makes paint more pliable, but it doesn't feel any thinner. it also doesn't smell like it's giving me cancer.
Having a plan really helped me here. while working into dry paint is still a challenge, only concentrating on one area meant I wasn't as concerned with the overall look of the piece...so whatever I didn't get to on that first pass, whatever inconsistencies there were in the colors from wet to dry, I'd address that stuff later. It took me maybe 4 or 5 shortish sessions to get the first layer of the face done here, and although I did go back in and add detail and glazing, It didn't require much more than normal. taking my time with each session made for less corrections at the end I suppose.
It occurs to me now that a proper step-by-step of the painting would really help illustrate all this rambling, but I didn't think of that ahead of time. I'm going to do another portrait with this same process and I'll do my best to document each stage. until then, I was really happy with this little experiment. I feel like I learned a lot about working into dry paint, and while I wasn't necessarily trying to paint tighter and/or more realistic, I like how it came out.