If you give the female or the Ditto an Everstone, there's a 50% chance the egg will have that nature. You can't pick a nature, but you can get one to have a 50% chance, if you want. It's potentially a benefit of hatching over SRing.
I like the calculator suggestion, and I've been using that. I've had 141 Drifloon since I started counting with the calculator, but then I decided to switch over and hunt in Ruby on the route before the Rusturf tunnel. I've had 241 Nincada/Zigzagoon/Taillow/Whismur/Skitty. It's easy to count how many REs I get there, too, by using the PP values. The pokemon I'm having kill all the pokemon on the route has 80 PP, so every time I have to go to the PokeCenter I can add 80 to the total.
On SRing you can use Synchronize. It has the same effect as the Everstone. If you have a Timid Pokemon with Synchronize at the front of your Pokemon, there is a 50% chance the Pokemon you catch will be Timid.
The Everstone method doesn't work with the Masuda Method though.