Wow, I find painting portraits to be an awesome experience. Starting with a blank canvas you begin to create when you put the pencil to work. My first portrait was a baby in oils. Oils work best with portraits because they take hours and sometimes days to dry giving you the time to work with them adjusting skin tone, light and shade. Remember to always start with three shades to every colour you use. Mix your colour, this is your dark shade, separate a portion and add a little white to it, this is your medium shade, then take some white and add a little of the dark shade now you have your lightest tone.
The medium shade is likely to be the tone you will use the most, with the darker shades for the shadow effects and the light tone in areas touched by light. Look at your photo or model carefully as you mark these areas on your portrait. Always soften the edges of your colours so they appear to blend into the next colour and not end abruptly leaving sharp edges. Don’t over blend or work the edges of your colours or they will end up runnning into each other. Continue to work on the skin areas building the character of your portrait with every layer you apply.
Depending on how much time you have to spend on your painting it could take anything from a few days to a few months to complete. Just be patient the end result will be well worth it.
Have Fun 