The plywood cutout works and if you have the $ the remote silhouettes are ideal. A bird launcher placed in front of the silhouette is used to launch a pigeon at the moment the dog being trained shows awareness that there is another dog on point. Through repetition the dog will learn to honor because it will come to expect a flushing bird when it encounters another dog on point. Once your dog is whoa trained the process is fairly quick to teach/ further strengthen honoring.
Another method I use prior to the honoring training is throwing a paint roller in the air while the dog is running toward me. Upon release I whoa the dog. This is critical especially in testing when the dog must point every bird encountered- planted or flushed. The bird taking to the air will signal the dog to point/whoa. Once the honoring training begins the dog will already understand it must stop when it encounters a flushing bird and then will associate the other dog on point as being the same.