Hand position is a deep topic, as it may lead us very far beyond sore knuckles, but 'I'll try to stay focused on this aspect.
According to Sega Sidibe, the positions showed in the Mamady Keita video is a ballet evolution.
Ballets dramatically changed the nature of djembe drumming (well, it's hard to stay focused...
), by transforming collective events, lasting for hours, into a performance, designed to fit the western theatre standards. Pieces were created, favoring spectacular effects, as a kind of competition between the different ballets occured straight away.
These evolutions can be summarized as playing faster, louder, and introducing arrangements, choregraphy and orchestration.
To be able to play faster, the shifting of hand position traditionally used to obtain the sounds became a handicap, and that's why the hand position evolved - in the ballets.
You cannot get the "old" slap sound of malian traditional drumming (I never went to Guinea) without advancing your hand about one inch. You cannot displace your hand properly while playing if you turn it inward like shown on the video; it's a whole different technique.
You can see it in this Sega Cisse video playing Sugu (Suku), it's especially obvious in the end, when he plays the chauffe.
Sega Sidibe is from Wasulun (south of Mali) and I think Sega Cisse is from Fuladugu (northwest of Bamako), it's not an individual or regional particularity.
EDIT: The video cannot be displayed
The bamanan name of the sounds validate this: Duguma kan, Sanfe kan, Cemance kan.
People often misunderstand these names because they think they refer to the pitch, while they simply describe the hand position:
- duguma kan could be translated as bottom, lower, on the ground - sound. => the bass
- cemance kan: the middle sound => the slap
- sanfe kan: the upper sound => the tone
Back to the topic: Here are my 2c advices. It's not anormal to feel pain when beginning, a single bad beating can be enough to hurt your hand.
But, don't abuse the djembe. Learn to play clear sounds relaxed, without strength, with good hand positions, You will preserve your hands, your ears, and the music.
I've seen many drummers having to stop playing for a while to heal their hands, I've seen many drummers with ear troubles (using ear protection is not a solution, because You will keep playing uselessly loud, and people who come to hear You play, generally indoor, won't necessarily have ear protections - especially the children).
I've seen many drummers with kind of soles in their hands, but look at Mamady Keita's hands, Sega Sidibe's hands, they have no such things.