There are a couple of approaches in SU that I use. Both pretty simple.
With either I take an overhead photo of the object/drawing. Step stool, standing if you can fit it in the frame, whatever. I try to be directly overhead to minimize distortion.
I then import this image in to SU (file, import)
Then using your baluster example, you can measure the actual baluster length and width. Draw a rectangle that size and scale the photo so that the baluster fits in that rectangle. The photo will come in as a group.
OR.. often times its easier to draw a rectangle the size of your balluster, make IT a group, then make a copy (hold down CTRL with the move tool) now move the copy onto your imported image which will come in much larger than actual size. Scale to match the image only using the corners of the scale tool (so the ratio of length to width remains constant). Once you have the rectangle over the image you can open the group and begin to add the geometry of the baluster in the image.
When your done you exit the group, and scale the entire group back down to the size of the original rectangle you made again only using the corners to maintain aspect ratio.
Feel free to message me if needed. Its a relatively easy process.