asterisk training

Hello - I am looking for a training course that teaches how to do use Asterisk + Freepbx + A2billing. Tell me how about the training it will be ( video, online, etc .... ) and also about the duration it will take. Please note that i already got some good knowledge on asterisk + freepbx + a2billing, i want to learn more to pass certification. Looking to get this started sooner rather than later. PMB me for more details. Thank you.