I too wonder how will he give instructions between rounds. Obviously he won't be the one taking out the mouthpiece etc.

As far as his skill level....it's not a requirement, let alone a prerequisite to being a great trainer.
Props to the journeyman fighter Freddie Roach that developed Pacquiao's right hand. After his loss to Morales, he was written off as a one handed fighter.

Props to D'amato ...amateur fighter who never turned pro.
Props to Enzo Calzaghe a friggin jazz musician trained Joe to a potential legend.

Sometimes the worst coach, trainer is the one who became a champ.
Be it Magic Johnson, Isaiah Thomas, Larry Bird per NBA...who all admitted ..being a champ didn't mean you can coach/train others to become that.

Roy Jones Jr, to Pernell Whitaker failed miserably.

If Paul can prevent his handicap from being an issue, he may be the one to detect holes, flaws...that he himself fail victim to...for the love of a good fight I assume!!!!!