Animation is time consuming, but Cassie Urban, one of Powerhouse Animation's artists, shares a few tricks--including Place and Trace--that she utilizes in her process.
Links for Animation Reference:
https://sakuga.yshi.org/
http://www.penciltestdepot.com/
http://framexframe.tumblr.com/
http://livlily.blogspot.com/
Check out more ProTips at:
http://www.powerhouseanimation.com/protips/
