Jorge Garcia-Segovia,
In my humble opinion, estimating more or less any animals age or size in the thick rainforests can be a huge challenge even for the trained eye.
If you take a look at some of the elephant trophy photos from Cameroon, you will see that they do shoot some quite young animals but also a fair amount of old ones. I do believe it is important to take into account what could be described as the "rain forest hunters mentality". Basically meaning that when you're in the middle of all that thick stuff, and an opportunity presents itself, decisions will have to be made rapidly. If it looks good at first sight you take the shot rather than letting a hard-earned opportunity slip away. I think most people that have hunted the rain forest can recognize this way of thinking.
As with any other animal, there are a few ground rules that ought to be kept in the back of ones head during the pursuit. When it comes to the elephant, they never stop growing throughout their lifetime so the sheer size is a good indicator of age. Now, since you're going to hunt in the rain forest you should probably work on the supposition that you won't be able to see the whole animal. It might just be a small patch of grey among the leaves or a bit more if you're lucky.
Any good PH that is somewhat familiar with the area he is hunting in should be able to point out the different clues that tells him whether the animal is a good trophy or not. If you've seen a lot of elephants in the forest you know what a big one looks like in comparison to a small or medium-sized one. Its tracks too can tell us a great deal about what the animal we're following is like.
Does the track and the pattern on the soles look worn down? How does the elephant behave while moving through the forest? Does he stop and urinate a lot? Does he stop to check the wind often? How well can he chew his food? How torn are his ears? Are his tusks really pointy or blunt etc etc...
These are only a few things that I could come up with now, just to give you an idea about what to take into consideration when trying to estimate an elephants age under tough conditions. I bet your PH will have quite a few tricks of his own to show you too
Enjoy your hunt and be careful!
Regards/ Erik Nyman