I keep the tank in the water bath during all tempered steps. I fill it until the chemicals are about halfway up the funnel so that the film is submerged but there's still some room. With the rubber lid on it will float upright, which I like, and I take it out briefly for inversions every 30s. Better temperature control can be achieved by filling it all the way up so that the tank sinks, but my tanks are leaky at times so I avoid this.
Originally Posted by TheToadMen
If you're going to have the tank float you also have the option of using the little spindle to agitate it so that you don't even have to take the tank out. Entirely up to you.
The tetanal kit is three baths and uses blix, but as other people have pointed out you're better using separate bleach/fix solutions. Any colour film that's particularly important to me I have done at a professional lab, but for my fun snapshots these kits are more than enough (and are just as good if not better than your typical grocery store processing).
Regardless, have a go with it. There's so much lore around about how tricky C-41 can be, but it really isn't any more complicated than doing B&W. Pay attention to what you're doing and have fun---I had a great feeling of accomplishment when I saw my first roll come out.