De-interlace or not to De-interlace

[Yev Belman]

I am new to compositing so hopefully somebody can enlighten me... From reading the previous posts I am convinced that Interlaced, Lower Field First is the way to finish a project. But what do i do in the middle of all the composition renders? Here's a couple of good example of what I am mostly interested in:

Take an interlaced clip, retime it in say Twixtor and end up with a 23.976 fps progressive composition. Do I render it out fields off? or back to interlaced with WWSSW setting? What is the answer if that is the end of my project? what is the answer if I now want to take the render and place it into my next Comp/project ?

And then, if i use this newly created progressive 23.976 clip, how do i use it along with my other raw clips, which are still 29.97, interlaced?

I get really confused and end up with skipping frames, jitter, etc :) Still learning.

Hope this is not too much of an AE question. Guess this was in the same lines as the conversation above.

Thanks.