Often a branch on a bonsai is too thin. To thicken it allow it to grow wildly without trimming it back. Keep the rest of the tree trimmed as normal.
Once the branch is of the proper thickness it can be shortened back and proper taper and ramification can be developed.
The definitive reference work on Ficus
for bonsai. The book is a softcover, 8 by 10 inch volume, with 144 color pages, containing detailed information for the beginner as well as the advanced hobbyist.