If I were to buy BTC using Coinbase, how simple would it be to move some percentage of it into an offline wallet?
Well it would take probably two mouse clicks and 2-3 clicks on keyboard. 
Why would you think it would be somewhat difficult?Bitcoin is VERY easy to use, you should try to USE it. You learned a lot by reading but u lacking practice. Buy 5$ of bitcoin on coinbase for example and send it to your software wallet. Easy-peasy.