The best method of treating Trigger finger is to have laser to the nodule. You can feel the decrease in size of the nodule as you go on with the treatment for 2 or 3 sittings. Ultrasound is also found to be effective. One of the main factor which hindres here is his occupation which may have lead to trigger finger. Position he used to keep his pen or any of his tool should be ruled out.
Hope this will improve the condition a lot. This was my perspective , it may be wrong.