starbuck3733t,
I'll let you in on a little secret... 90% of my work is designing it ahead of time.
(Even HOW I'm going to machine it) If I didn't lay it out first... I'd bugger it up for sure.
As to my milling practices... I've been working with power tools since I was 6 years old. (Nearly 29 years now) So, I've gotten a lot of this down by feel.
After a certain amount of experience, you begin to learn when the machine is taking too much material, or not enough. I am still learning on the mill... once in a while, even with proper application of oil, I get a bit that starts to "chatter" on me... and I have to back off.
If all you have is a hand tools and/or drill press, you can still do some amazing things. Plan it out, figure out what you can and can't do and work around it.
In theory I could have made the video block solution out of multiple sheets of copper clamped together in the oven (with metal C-clamps and steel plate pieces) and a simple drill press. It would have been more work, but could have been done.
End mills can be used in a drill press, just don't expect the same accuracy. And you have to use different techniques (Plunge Roughing instead of milling a channel normally for instance).
Never underestimate what you can do. If it seems impossible... ask here. There is a wealth of information at your fingertips and people willing to share their knowledge with you. AND ... there are always multiple ways to achive the same resulting design. (Just look at what BladeRunner did with hand tools for that
hard drive cooler on his site
)