I have been doing my own C-41 for about 18 months now, mostly because it's a PITA to get my C-41 120 / 220 films done where I live. Plus, I like the alchemy and magic involved.
It is no harder than doing B&W processing -- in fact, I agree with mackinaw, it's almost easier than doing B&W.
Here's my process, from start to finish.
1. Prepare a picnic cooler (the ones made of hard plastic, that have insulation for keeping drinks cool, about 10L / 10 quarts in volume), and fill it with warm tap water. Use a thermometer to approximate 38 deg C. Place the bottles of pre-mixed C-41 chemicals inside the bath.
2. While the chems are warming up, I assemble the Paterson tanks & reels that I need (dry, not wet). I then head into my bathroom and load the films as normal.
3. I bring the loaded Paterson tanks to the sink. I pre-warm the tanks (with film inside) with warm tap water for 1-2 minutes.
4. I pour out the tap water from the Paterson tanks. I remove the bottles of C-41 chemicals from the picnic cooler, and set them on the counter. I double check the temp of the bath water, to make sure it's at or near 38 deg C.
5. I begin processing as per the kit directions. This is where things are a little tricky. The timing and temps are somewhat critical here, and 3'15" doesn't give you a lot of time for fudging around. I agitate for the 1st 30 seconds, then let the Paterson tank rest in the bath, then agitate again for 10 seconds every minute.
6. I rinse with warm tap water between dev and blix stages. The blix is easily contaminated by the developer, and will supposedly lose effectiveness very quickly, so I just do a quick rinse to be sure.
7. Temps on the blix and flo stages are much less critical than the dev stage. I relax at this point and enjoy the harsh, carcinogenic fumes of the blix. It's usually at this point where I question my sanity and wonder why I do this at all. 🙂
8. Results? The first few rolls of fresh chemistry are always spectacular. I have tried using the same batch of C-41 chemicals for 10 rolls or so, but found that the quality started to diminish. I tend to just mix up what I need for 3-4 rolls, and use it right away. I don't think the C-41 chems keep very well once they've been mixed.
My experience has led me to believe that the 38 deg C / 100F temperature point is very important but it's not a make-or-break kind of thing. I've accidentally developed at 40 deg C, and it's been fine. The modern C-41 chemistry is reasonably forgiving.
Good luck with your C-41 adventures.