I've tried your suggestion over the past few weeks and it's not really practical because it is too time consuming. CSS Form Builder is simply not a good option for responsive forms- too much work involved. Despite this, I've developed a workaround using Twitter Bootstrap which has beautiful form styling built in. I build the form as usual using CSS Form Builder. I then remove the WebAssist CSS link from the page and Bootstrap's default form styling kicks in. With some very minor html adjustments, removing the <ul> and <li> tags for instance, the Bootstrap form styling looks beautiful and it's responsive.
The end result looks and works well but I'd like to get rid of all the unecessary classes and styling code that CSS Form Builder creates. Is there an easy way to strip out the styling when building the form in CSS Form Builder?