Wraparound camouflage...Any tips?

If I understand your camo pattern correctly, what I have done in similar situations is to take a strip of paper, wrap it around the part, and then draw the camo line on the paper.  Then after taking of the paper you now have a flat template that can be used for cutting out a tape mask.  If the edge line where the ends meet doesn't look quite continuous, a small bit of tape can be used to span the joint and blend the line.

For masking, I always use Tamiya Yellow tape.  It cuts really well, is extremely thin and flexible, seals well but doesn't lift up the undercoat. 

I picked mine up at WalMart, about $1.00 for enough to do several planes.

When doing a difficult scheme like that, I use handi tack, a silly-putty like substance.  I roll it into long thin tubes, then lay it on the model to mask.  I fill in any open spots with more handi tack or tamiya masking tape.  Here's how it looks ready to paint:

And after painting and removing masking material:

Hope it helps!