Welcome to the Strelets Forum. Please feel free to discuss any aspect of 1/72 scale plastic figures, not simply Strelets. If you have any questions about our products then we will answer them here.
have a look at www.coolminiornot.com. There you can find a lot of hints how to paint flesh, from simple to advanced techniques, in the right bar under "articles".
Simply spoken: use a light flesh color as a basing, and then give it a thin washing with a middle dark brown (siena e.g.). This works in 1/72 in a satisfying manner. for more strong faces use a darker greenish brown, umbra . I dont know the humbrol names.
For a more advanced skin use a mix of red, white and yellow - so you can make your own skin color, which can be darkened with umbra or a carefull used dark blue. Don´t use black.
There are many ways to approach painting skin. I usually (after priming) give the area a thin medium brown, followed by drybrushed light brown, then skin colour, and finally, a thin red-brown wash. It sounds complicated, but if you do a bunch at once it wont be as bad. Mr. Kupski's way works exceptionally well too, as you can see on Hat's Everything Toy Soldiers page.