How do. You quicken the thickness of a starter plant. Do you keep cutting the end off or let it continue o grow?

The answer is a little complex so the best thing for me to do is refer you to this article.

www.bonsaiempire.com/blog/bonsai-trunk-creation

Okay, after re-reading your question it is to let it grow.

Just remember, speed is not everything. A slower proces with more cutting back will in the long run probably give you the better bonsai with less scarring.