My suggestion is to first go simple with cutting and once you get the knack then look for improved approaches. First forget about precise angular descriptions. Look at the rafter, note that: tail is reduced parallel to rafter slope, a cog abutment is at right angle to slope and full dimension rafter beds at slope. So a simple cutting scheme requires a control from slope and cuts square and parallel to control.

So begin with cutting the bed for the rafter tail, you will need a handsaw, chisel, hatchet, slick and combination square. Working to the lines, saw to the shoulders, then chip out waste, and smooth the bed, all the while retaining sharply laid out lines. The next cuts can be controlled with the combo square working against the tail bed.

You will quickly gain the feel of the shape