tips or tricks for masking a 2 tone paint job?

Since the line is the border between two colors, it ordinarily is not noticable.  The only thing that is noticable is when you accidently cut away (into tape you will be pulling up) from your original, intended line (a mistake).  When you go back and cut again, you have an extra line that will not be on the final border.  Since the normal order of masking is to paint lighter colors first, then mask, your extra cut is in the lighter color and will be more visible.  So you must take care to cut along the line exactly, else you will have a crack that must be sanded and repainted.

Print scale plans. Either with the scheme already in place or draw it on yourself. Tape this down over tape. Cut. Viola...

A better plan is to eyeball the line with blue tape to within an 1/8" or so of where it goes. Then take 1/4" Tamiya tape and freehand the final line with it.

Hello;

I just finished my Hasagawa P40E with the dark green and dark earth camo on top and it came out very well. Now I dont know if how I did it was inovative but here goes. I have some green paiters tape that came from Menards, cant remember the brand but its nice and thin. I enlarged the camo pattern on the plans to 1/48 and cut out the patterns that were to remain dark earth. I have a white waxed paper that I put lengths of the painters tape on and then using a glue stick I attached the patterns. After cutting out the patterns I peeled off the waxed paper and placed them on the model. It was nice to have the panel lines on the pattern to help aline it on the model. This my first camo pattern like this and it was very easy to do this way. 

Bill

Like Don said, you can layer the tape to give yourself a sheet for say a wing half of fuselage side. You could also look at flexible vinyl pinstiping tape as used in the automotive game or cutting regular masking tape into very thin strips so that it becomes more conformable.

What I do is draw a pencil line on the tape.  Then remove the tape and cut along the line.  Then put the tape back on the model.

Don