Great answer sis mawaddah. Masha Allah. But still you couldnt tell me HOW to comb my hair if in the future I have long hair :X . If thees no expanation from hadith then maybe you or sis amirah or sis sawal -hafidhahumullah- or any of my brothers -hafidhakallah- can tell me how those Yemenis used to comb their hair insha Allah.

I was doing some research for you on this Brother since you asked and this is the conclusion I came up with Baarakallahu Feek.
Well, according to Ulama such as Ibn Uthaimeen, Ibn Abdul Barr and others Rahimahullah, Growing the hair long is NOT a Sunnah for which the person will get reward for (Subhanallah I didn't know this!!) because there are ahaadeeth which report that Rasululllah peace be upon him shaved his head,or grew it long, or kept it short ,Ahadeeth came that his hair was until his shoulders, or between his ears and shoulders or until his earlobes, and there was no command for anyone to grow their hair long.
Sheikh Ibn Uthaimeen also said that if a person wants to keep his hair long, he should not do it under the claim of "following the sunnah" since this is not a sunnah, but rather it was only a practise and a tradition of those days and one who grows his hair long is NOT rewarded for it.
Ibn Abdul Barr stated also that if it has become from the custom of the foolish and the people with no Akhlaaq to keep their hair long, then one must not keep their hair long otherwise he might resemble these foolish people. Rasulullah said
"Whoever resembles a people then he is from them"
Also another thing about keeping hair long is braiding the hair, There is a hadeeth which stated that Rasulullah entered Makkah and his hair was in four braids. The Ulama said that most probably it was only combed this way because Rasulullah was on a long travel and thus kept his hair in braids since he would not have time to attend to it whilst on travel Wallahu A'lam.But there is nothing wrong with braiding the hair in times other than travel also, as long as it is not against the normal customs of the people of the country.
As for
HOW to comb your hair if you keep it long Brother, Then it does not matter how you do it as long as you keep your hair neat and orderly Insha'allah

and this is a
MUST for whoever has hair because Rasulullah said
"Whoever has hair then let him take care of it"
However there is no hadeeth which mentions that women must comb their hair in a certain way and men should comb their hair in a different way, so we must not make it difficult upon ourselves and try to put rulings on ourselves which are not there. Simply comb your hair like how anyone with long hair would comb their hair.
As for how the Yemenis used to comb their hair....welll........from my experience in Yemen, I have never seen a Yemeni man with long hair. In fact it was the custom and tradition of Yemeni men to keep veryyyyyy short hair or to just be bald
So Akhi, just comb your hair as how you would normally comb your hair, if you wish to dye it then you may dye it, you can keep it long or short or bald or whichever way just as long as it is not going against Islam in anyway Insha'allah and is not imitating any bad customs.
Wallahu A'lam.