Hi Minh,
I'm glad to hear about your new setup and especially to see the confidence you're developing. You're starting out the best way. It's hard to make a drawing or painting look realistic when someone has only worked from photos.
I also use my cast as a reference when I have to paint from a photo. I try to replicate the lighting and angle so it will be similar the man I'm painting. There is such a diffence between working from a photo and a 3 dimensional reference. Now if I can find a cast of a child - my kids are tired of being models!
Keep up the great work!
Renee