#Template
Ralph's reply is one way to do it. Here's another:
Load the picture you want to trace over. It can be a complete image. Clip a
copy of it to the Swap buffer. Click on the right frame arrow to either move to
the next frame or _attempt_ to move to the next frame. (You don't have to have
a 2nd frame. This step simply clears the Change buffer.)
Now, paint away over the picture. You can use Scrape ink if you need to undo
anything.
When you've finished your tracing, select Clip Changes from the Trace menu.
This will put all changes you've made in the cel buffer.
Clear the screen, and then paste the cel with your changes.
Another, more obscure and problematic way to do it is to turn on the Create
Mask option just before you start tracing. When you're through, turn on the
mask, and you can erase everything but the portions you drew (which created a
mask while you were making them).
There's probably also a way to do it with XOR ink, but someone else will have
to come up with that.
– Jack