My guy is all-natural, and the only thing I do is trim the tips of his tail once a year (autumn) so that his tail doesn't get too muddy during the mud season. I also used to trim his mane until I got a satisfying result, because he had rubbed out large sections of it in his previous stable and it had to be levelled a bit.
I believe that whiskers, eyelashes, ear hair, feathering, etc. are there for a reason, so I see no sense in trimming it all off. However, I don't show, so I don't have a reason to do so.
I have come a long way, to surrender my shadow to the shadow of my horse.