Absolutely do not use your 1/8" rulers for ruler quilting. It is dangerous and scary. If the ruler slips under the foot (which it will) it can chip the ruler, throw out the timing, and possibly result in injury to an eye or a finger.
There are lots of youtube videos and classes on how to do ruler quilting on both domestic sewing machines and longarms. Craftsy has classes. I've accumulated a huge assortment of rulers of different shapes and sizes for use with my longarm. The clear plexiglass allows you to see through the ruler to the quilt, and they often have etching that helps in aligning the ruler for a more precise quilting pattern. Most rulers are 1/4" thick, but a few for the longarm are 3/8".