Painter has a ready facility to make tracing from an existing image very easy. They call it "Cloning," though I have no idea why. It's really just being able to take an existing image, put it in the background of the image your painting, turning it's opacity down (as if it were behind tracing paper), and then drawing/painting on top of it.
There's a few finicky aspects to it. It works best when the image your tracing/cloning is exactly the same size as your drawing/painting. So, take the image you want to trace, and use Photoshop (or whatever image editing tool your comfortable with) to set your image to the same size, in pixels, as the image you want to create in Painter. So, if you're working on a Painter file that's 10x8 inches at 150 pixels per inch, your image will be 1500 pixels (10 x 150) by 1200 pixels (8 x 150)
Create a new document in Photoshop that's 1500 x 1200 pixels, then copy and paste your source image into the new Photoshop file. Then choose Menu > Edit > Transform to scale and position the pasted source image in the new photoshop file. Save it (Painter can read most Photoshop files).
My image, scaled to 1500x1200:
In Painter, have your 1500x1200 file open, then choose Menu > Window > Clone Source and this panel will appear
Click on the little disk (who uses disks anymore?) icon and choose "Open Source..." Choose your tracing image from the file dialog
Click on the tracing icon to turn the image on
Note that this panel loves to disappear. Control/Command 6 brings it back.
Cloned image turned on
Build up with light strokes
Add in middle values
Add in background
Add in details
Finalize with eraser details
A variation with Blender brush