Always do a value study of what you like immediately.
Use this value study to block in your painting with the values in similar but darker colors that the true color.Check your design for lines to the focal point, does your eye move around the painting? No tangents,etc.
Do not follow the light. Keep your highlights the same as when you first viewed them as the light changes so fast.
Block in the color values.
Step back 15 to 30 feet and view the painting at this stage and make sure it WORKS! View in a mirror to catch any lines that are off or color values not true.
When this is all done, then and only then do you fill in the light values on top of the dark and think about the details. The secret is to wait and be patient for the base must be there before you can do the details. The painting should work without the details from a distance.