You don't want me to say it but I'm going to anyway: draw, draw, draw! I feel you, you're sick of 'just drawing'. But hey, you want to be an impressive painter? Learn to draw first--then practice until, well, your hands stop working. Portrait painting can be unlike painting anything else--you may be going for a 'figurative' look and be satisfied with that--but if you want the piece to be recognizable, you're going to have move past the 'blocking' stage and get to the details. Here's a great way to get geared up to do just that!
Sick of your pencil? Not to worry--there is a way to draw with your paintbrush, too! Not as easy to carry, and yes, you've got to have some water and a few other tools nearby, but the experience can help you move forward and avoid the 'boring' factor of repetitive lines.
Here's an exercise I've used with some of my students as a warm up in our 'drawing class'. It brought about smiles and enthusiasm for the piece we were working on and forewent the 'sigh' of pulling out the pencils.
We used watercolor to sketch and draw with. The results were more than impressive!
A. Initial Sketch
We start with a blank piece of paper--no pencil guidelines to follow. Then begins our blocking phase and instead of small, graphite lines, we use a round watercolor brush (sz. 6 for our 11" x14" area, almost dry), to create large shape areas. There is no need to worry about hue at this point so I'm not going to cover that. This exercise is for your brain to accurately interpret what it's seeing and portray that 3-D shape onto a 2-D object.--with a different medium than you've been using.
I have found that negative drawing works wonders for getting your brain in the correct 'art mode', and I encourage such with my students to find the negative spaces and concentrate on them. I try to follow a path of continuously smaller shapes and values paying close attention to how they interact with each other. We draw all over he paper 'blocking in' the shapes that are found. Remember, this is an exercise for getting your brain ready to paint accurately and you shouldn't give up if your 'exercise' doesn't give you immediate results. It takes time and practice.
Here's a tip: If you find you are getting 'stuck' on a certain area stop yourself. Focus your brain on the activity at hand--the negative shapes, and the feel of the brush in your hand as you trace your shapes onto the paper.