As had been said, there is no point in being critical until the canvas is covered. You cannot make good relational judgements until all the parts are there. When you have covered the canvas get out your calipers and start measuring. Bump this a milimeter, bump that a milimeter, double check the values, extend a shadow or a highlight and boom, you gotta painting. The finishing process can take as long as the prep and the initial coat. You should not even be considering the likeness yet. All you are concerned with is the two dimensional shapes in front of you, and the values. This much of that color in that darkness from here to there, across to there and back down. Just keep going and go sloooow.
I have finally taken the time to make the followup video to my Jenison Device retest video from two years ago. I needed two years of learning and experience to make it as you will see. If you are interested in a lazy Saturday afternoon goof and would like some entertainment, go watch me opine. As a bonus, there is a full scale view of my studio and the happy family project.
Sure Ronna, he would be ok, it's just a bunch more to paint. A portrait is really no harder to paint than anything else but getting past the psychological barrier can be a test. Making the first one as easy as possible helps to overcome it.
Thanks @Forgiveness. I have had a lot of fun getting my studio right. I owe a lot to @summer. And @megans. The light difference is fantastic and I have also had to be very careful of what I wear to paint. Next for me is a better laminator. My laminate throws a lot of reflections at me. Mark's did not, so I want one of his.