First off, shaving in the shower is a really bad habit. You should work on breaking it asap. With straights ( especially while learning ) it makes it hard to get your angle right. It also exposes your straight to a lot of water, which may be the reason your having a problem with rust. The water permiates the scales and causes that area to rust quickly. As far as the brand and size go, it really is a matter of preference. I prefer dovo to TI ( no offense meant for our TI fans ) and 5/8 is my favorite size, followed my 6/8. It really all comes down to you. What do you prefer? As the years go by you'll probably develop a collection allowing you to wake up in the morning and pick a razor that suits your mood for that day. If you do decide to purchase another razor I'd recommend buying a razor that is different than the one you have, both in brand and size. Experiment with it. That's a lot of the fun in this. And it what helps you learn what your personal preferences are.