I always struggle with drawing and line work... so im trying out a new technique someone told me. Start with a QUICK small speed painting, just black and white on grey (minimum detail - 20mins or less), to determine your artwork, even if you need to do a few options because like me you cant decide on one specific idea. (this process allows you to try many different ideas in a short amount of time)
Then from your group of paintings, you can choose your best/favourite and then blow it up and start to create linework for it adding in all the details and then pretty much start the painting from scratch. Atleast now you will be happy with your choice and the would have already explored your other ideas.
Well, make sure to practice a bunch and put yourself on a timer. Once you decide on how much time you want to give yourself, make sure that you DO NOT go over that time.. Once you run out of time, start something new. Do go back and fix it. Its important you remember how much you can create in a given time. Your mind will get used to the pressure.
Another thing to work on is pushing your internal visualizing skills. Find the mood of your piece, jump into the world you are about to create. Think of the key words, the color, the genres, the music, and your attitude when you want to create this new work. Your mind can be trained to do this part incredibly fast and thus guide your work in a good direction before you have even made one stroke on the canvas.
Just a minor note, sometimes..sometimes if you stick to anything too specific while visualizing, it can hinder your creative side. Thats why I mentioned more vague things above to set your mood. Imean if you already have a design idea for a specific object, thats great...but remember being so fixed one part of the picture, that I ended up spending forever on making the other parts fit in.