Teaching Inquiry: What approaches can I take to help struggling students overcome writing difficulties and enhance their motivation to write?

Today I narrowed down the focus for my teaching inquiry.  Based on my data, my urgent focus needs to be around developing writing.  In order to begin the inquiry into my teaching practice I needed to think about my inquiry question. 

Originally I thought forming the question would be quite simple.  My initial question was 'What can I do to improve the achievement levels of my struggling writers?' however on reflection, I found this was extremely broad and more about what I wanted to achieve at the end of my inquiry.  So today during our staff meeting, I worked with a group of teachers who all wanted to work on improving the achievement levels of struggling writers.  After a bit of discussion, I found I first of all need to work out what is causing my students to struggle with writing, then work on strategies/interventions/direct acts of teaching, etc which will help these students to overcome these identified barriers.  A large proportion of my identified struggling writers are also boys, so a lot of my inquiry will probably involve focusing on finding out how boys learn best, and how I can motivate boys to write more quality pieces.

Keeping this is mind, I formed my new question which is:
'What approaches can I take to help struggling students overcome writing difficulties and enhance their motivation to write?

My initial thinking is that if I can help students overcome the challenges/barriers to learning such as handwriting, spelling, lack of ideas, topics, self belief,  etc, then hopefully the students will become more motivated during writing, and become more willing to put their ideas on paper.  If I can also identify what the barriers are, and the causes of these barriers, then maybe I will need to make some changes in teaching practices across all curriculum areas.