reading
not saying its necessary but ive noticed my ability to visualize has improved. 
read neuromancer if you like sci fi, its the most visually descriptive book ive come across. 
the beauty of words is that we all imagine things differently. when using visual reference we often limit ourselves with how far out we go. 
reading helps establish a vision/feeling that you can then seek reference for.

how to relinquish control
lose yourself not by erasing who you are, but by becoming so deeply entwined with your work that the boundary between creator and creation no longer exists.
authenticity is the most important part of any creation. If your art lacks souls its dead. no amount of technicality or "skill" can give you this.
relinquishing control is to be free of fear, this is just as much of a skill as anything. 
you have to trust your gut visceral response. you cant say you dont have one because everyone does, as long as you have an internal dialogue i guess. 
you have to train/allow yourself to feel it. this can only exist without thinking and thats the hardest part. its similar to the form of meditation that allows your mind to wander without force. 
being an artist is the ability to pick the good out of the bad and mediocre ideas. without trusting yourself those bad ideas will never be acted upon. 
in the beginning its obvious your work will be bad as any new skill is, unforunatley youre an adult so the chances of you making art free of control like a child is zero.
picasso was straight up delusional, that shit was nothing like a child bruh. no adult will ever come close to creating art like a child because to make it you have to BE a child. pure, innocent, fragile etc etc... 
following through with the bad ideas will train you to be far more creative than thinking or believing an idea is bad. the master has failed more times than you have tried. stopping yourself from failing is worse than actually failing.
discipline isnt waking up at 7am and running 10 miles. its having the strength to follow you through with an idea you decided on. when things get tough, starting something new will always look like a greener pasture. you have to finish.

how to use reference
use what you see as a guide not a rule.
dont be a slave. change shapes, colors etc..
learn how to use it to further the vision or idea instead of just copying what you see.
if you have a familiar grasp of something you should always be taking creative liberty, this will bring you closer to who you are. leave the 1to1 copies for master studies and trying to understand something complex like anatomy or machinery.