Solo Oshawott

I wanna do a Solo Oshawott playthrough of Black and I was wondering if you guys would like to suggest any rules for me to play by to make it harder and also how I should build my Oshawott with regards to what nature to get and whether or not I should EV train it, and if so- where?
I'm not entirely sure if I will evolve it past it's second form because I'm not sure what it's called but it's one of my favourites and I am not a big fan of the final evolution. This will also serve to make the game a bit harder.
I need good HM slaves, also. Although I will have 5 free spaces I would like to minimise HM Slaves. Bear in mind I want Flash (I think it is used in Black, no?).
This will be the first time I play to the post-game and I want it to be a challenge.
Any input appreciated.

Thanks in advance.

You can catch a Panpour early from shaking grass in Pinwheel Forest which can learn Cut, Surf, Dive and Waterfall. But you'll need to teach the Pansear that's given to you earlier in the game Cut, but after that you can box it.

Then, later on, you can catch a Golett which can learn Strength and Flash and then Fly when it evolves. If you need Fly before that, you can catch a Woobat which can also learn Flash.

But TBH, you only need Cut once and Strength a few times in the main story. Post-game you can catch a Golduck which can learn anything you need apart from Fly.