Plus, according to Serebii, it takes 100,000 watts to activate the course with Feebas and Spiritomb in it--that's like 300,000 steps. Since the Pokewalker notices when it's being violently shook and won't record steps in that situation, paint-can shakers are out of the question, and thus it's not very feasible to actually try getting that course unlocked to get them.
Plus you have to deal with the Pokewalker's annoying system... Even if you've gotten the 100k watts, only the next course will be unlocked on the cartridge, as only one new course will be unlocked at a time. So you'll have to keep transferring back and forth until they all actually show up.
Then you get to the Pokewalker's catching system: It takes 10 watts, or 30 steps, just for a shot at a Pokemon. Then, you have to make sure you're on top of things and respond to the exclamation points in the grass, or else the Pokemon will just run away and your watts would have been wasted. From there, you get to how the Pokemon you want isn't guaranteed by any stretch. Even if you do find it, you have to deal with a system that's like some sort of hybrid of normal catching and the Safari zones: you can choose to attack the Pokemon (both you and the wild Pokemon always start off with 4 health, with each attack that hits taking off 1 unit of health, and critical hits taking off 2), try to parry its attack (in which case you'll just dodge it's attack and hit it for one damage), or throw a Pokeball at it. Your attacks can miss (and if this happens, the wild Pokemon will probably still be hitting you, meaning you won't be able to catch it at minimal health without your Pokemon fainting first) and catching isn't guaranteed even at 1 bar of health. And if you throw a Pokeball, but it doesn't catch the Pokemon, it's practically guaranteed to run away. Luckily, the Pokemon at least don't run away when you're simply attacking them, but they have the chance to if you go with the parry option.
Put all that together, and you have quite an annoying system for trying to catch any particular Pokemon, especially since you'll have to keep recharging on watts if it doesn't show up (and the Watts that are automatically transfered over with your Pokemon when you're trying to unlock a course are stuck on the DS, at least from what I have seen, and thus aren't going to be helping you once you actually get to catching the Pokemon). Everything considered, not a way I'd recommend trying to use to get Pokemon for the marathon.
