It took my buddy Dan who placed 9th out 19 or 20 strongmen in the "Global Grip Challenge" this weekend months, I think close to a year to close the #3 now he can do it with his right or left. He would sand the ends of his #1and #2 down for a harder squeeze to prep for the #3. The grip machine sounds like it would help alot.
As for me I do lots of grip training, but never train grippers or bending and it shows because I have yet to close a #2 or bend a respectable nail.