I’ve been doing pullups for my entire life. One very important caveat is that it is EXTREMELY easy to hurt yourself. I have learned and relearned that lesson over many decades.
Yes, negatives are a great way to begin. They are also something that you can continue to do even when you can do consecutive pullups.
Up or down, take it slow. Pumping out rapid-fire pullups is foolish and one way to get hurt. The other way is straining, which is something that is so easy to do when your goal is ten and you are at nine and one half…
Just write down 9.5 even if it was 10 yesterday. Better that than having to drop back to five or all the way back to negatives.