The tutorials in Pixiv is very well really helpful. Usually when I'm bothered with something and need help, I just rush to pixiv site, type what I want to search (i.e. 着物の描き方<--how to draw kimono) and I'll find really helpful few tutorials I can never find in devART <.<
Another reason is, Pixiv has lots of PROFESSIONAL artists. One of the books I've bought for further digi-coloring knowledge is a book full of techniques by none other than great artists from Pixiv.
and the rest I cast amen on Keilis's comment xD
(also, if you are living in japan and aims to be professional, there are some contests, magazines and many helpful art resources that can help you find a job--or just improve your art for the best

