Glad to help if I can, Nuke..
First, it is always a good idea to have a hi-resolution image which you have adjusted for color,lighting,clarity.composition etc., before you start to paint.
Then, when you paint, it is important to choose the correct size brush with the proper opacity(strength level) in order to achieve the painterly effect without deforming(usually meaning smearing) the image.
Finally. when you have finished painting there are some filters that you can apply which enhance the painterly effect. The type of filter and how you apply it will usually depend on the paint program you are using. i.e.Photoshop,Corel etc.
There is a ton of other information that would probably be useful to you,but I hesitate to post it here without viewing the image you are painting.
If you post the image, we could start by directing your efforts on different sections of the painting. For example, how to paint the skin tones on different parts of the body.
There are also many free tutorials on the internet. Just google "smudge painting" and you will be gifted with an abundance of helpful information.
You can purchase basic smudge painting video tutorials at this site:
http://www.mmkgraphics.com/tutorials/virtualpaint.html
All the best,
Patre(Pat)