A lists of teachers from my gold-mining the internet :
gold - Feng Zhu website fengzhudesign.blogspot.ca , the best of the best. Make sure you checkout his design cinemas 1-50
silver - Paul foxton website www.learning-to-see.co.uk/ , he is an artist going back to drawing / painting thru self taught route . not only he can provide you with road maps , but he have two very helpful links www.thedictionaryofhumanform.c… free to download book www.learning-to-see.co.uk/comp… .
silver-sycra yasin website www.sycra.net
jason seiler ,blog jasonseilerillustration.blogsp…
bronze - On youtube there are -Myron Barnstone
these plus Conceptart.org will keep you busy for months.
There are much more valuable information out there , but this is a short lists and my own two cents