These are the slides from a 2.5 hour workshop I ran with 18 people at WordCamp Birmingham. We ran through creating a child theme, editing CSS and other tools used, dealing with parent theme CSS, and migrating complete WordPress installs.
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I charge sensible rates and take on creative, web and WordPress projects as a freelancer/consultant. I've also setup a new company called Wider at the start of 2016, which I'm channeling most of my work through now.