Hmmm... I think I was giving out unclear messages with my last comment... 8o)
Using line fader CAN (but not neccessary - I used the word "probably") give you a smoother mix.
Also, I assume that we all KNOW that a certain part of a mixer is NOT limited to any one purpose only. As an example, if people uses the line/phono toggle switch for just to toggle between sources, we would never had some of the cool transform and tip scratches... (Check out Dj Pumpin' Pete in the DMC 1991 US finals - he scraches really well with the toggle switch)
When it comes to mixing, it all depends on each individual styles. Some dj's like to cold cut the mix... which is fine... as long as your mix comes out sounding good - that's all it matters. But I idolize dj's such as Jeff Mills. I saw Jeff Mills several times. He uses 3 turntables and a Roland-909 drum machine. He constantly has 3 different tracks going on at the same time. He does all his tricks, in-out cutting, and mixing all with his line faders and gain knobs. And his mix is super tight.
So, I have to apologize for giving out the wrong impression in my last comment. Part of being a dj is being creative. So, be innovative - don't limit your thinking...
About transforming with a more shallow fade-in slope, I actually find it easier to transform with the STEEP fade-in slope - the transforming sounds a lot cleaner to me. Sometimes I even use the toggle switch to transform - it just sounds chrisper. The only Dj that I've seen that can scratch with the fader so chrisp that it sounds like he was using the toggle switch is dj Babu of the Beatjunkies and Dilated People. I saw him scratches live at a club in Chicago. It was so clean that I thought he'd pulled out a bottle of alcohol and clean his scratches with it!!! j/k 8o)
Anyways... Good luck and take care...