Estes Skylab #001973, Build, Part 25, Middle Section Wrap

After the center wrap black areas are outlined, the white areas are masked off.

I found it easier to cut 1" wide masking tape into 1/2" half strips. These are placed down the midline of the 1/8" wide (or so) black border lines.

The remaining white areas are covered with 1" wide masking tape.

Seal off the brown tape as best you can. You aren't relying on brown masking tape for the sharp black edges. 

Your black ink border lines should end up as your sharp color separations.

After you spray the black, the Sharpie border black may show up as a "blue/black" under direct, bright light. Most of that will disappear after brush touchups and a final dull or clear coat.

Use the dull coat after applying water slide decals. Decals transfer best onto glossy finishes.

Be ready - 

When the tape is lifted, you should have sharp masks -

you might find some bleeds as shown on the right.

There will be a lot of touchups.

Spray some of the same paint you used on the model in a small cup. Use a brush to clean things up.

TIP: Use a dedicated brush for each color. One brush for white, one for black and a third for silver.

If you touchup white paint with the same brush you used earlier with black paint, your touch up area could end up light gray! You can clean your brush between colors, but some previous residual paint can show up mixed in with the current color.