I also count my strides but if your horse won’t take off at the right time you can always use placing poles as well. (https://www.yourhorse.co.uk/advice/improve-your-riding/articles/2016/6/14/know-your-striding-part-7-placing-poles)
What I do is I count the strides before the jump, like 1, 2, 3, squeeze. It really helps me and my horse get the distance together and correctly.
The most important is the stride and the route. If you have a good rhythm and a good route before the jump, your horse will have the right stride and will take off at the right time ! :)