Also try to break the peices into bits about 1/2 or 1/3 of your finger nail. This will mean he gets his treat but doesnt get distracted by it and keeps his attention on you to get the next bit. It also means that you can train longer because he will not loose his food drive as quickly.
Can you give us an outline of your training procedure?
Try not to let yourself chop and change between training methods it could ge a bit confusing. You should make a training plan and stick to it. This is a great place to get help with that