Lay one piece of tape against the wood and press into place. If your carving is totally dry that tape will not remove any color when you peel it off. Place the second piece on the opposite side, press into place. Use your fingernail to crisp the intersection at the top and bottom of the two pieces so there is no gap.
Don’t use packing tape as it is extremely adhesive and hard to remove. Masking tape has a crepe paper backing and will leave very small gaps.
There is a tape system used in sign crafting for pin striping cars that is wonderful for this technique. This has two layers of tape – a large, clear tape and two to three finer tapes of Mylar which are placed on the adhesive side of the clear tape with a premeasured space between the smaller tapes. You place the tape onto your work where you want the strip, press into place, peel off the clear tape. This leaves behind the Mylar strips. You lay your color down the gap between the Mylar and after it dries remove the two strips.
You can also get frisket paper which is large rolls of adhesive backed plastic. You can press the frisket into place, then using an exacto knife cut stencil shapes. Apply your color, let dry, and peel.
pin striping tape
frisket paper
Allow each coat of paint to ‘tack over’, to lose its shiny, glossy look. That is dry enough to proceed to the next coat.