My grandfather worked in a Victorian joinery sweat shop. Had to make a four panel door in eight hours, all by hand. If not the sack, down the road, or as is said to day made redundant.
A trick he taut me to cut two sets of dovetails at once, with very little marking out.. After squaring the ends of the timbers, draw a line all around the thickness of the timber from the ends. Place the four timbers in the vice with the two outer pieces level with the thickness marks on the two inner, which are also level with each other. You could have drawn the tails on the inner pair. But I do as the old boys did and guess. Take a tennon saw ( a thin blade is wanted) lightly mark the top corner of the tail across the top, before cutting down dip the saw down to mark the outer pieces then cut down at the angle of the tail stopping as the outer pieces are just marked. When all tails are cut remove from the vice, cut the waste away with a copeing saw. Use the marks on the ends of the outer pieces to cut down for the fingers, removing the waste as before. All this done by eye, this is why the joints on the backs of old drawers are often uneven. Now you know why I am the Hammer.