Knowing how to properly mark behavior is critical to being effective and efficient! Your dog is the master at discovering patterns, and that means details matter. Your minor inconsistencies will translate into pattern disruptions that throw your dog off and drag out the process.
Also, most people only have positive markers. Stop giving your dog 50% of the information and expecting results. The word "no" is not a correction. And it isn't a marker until you teach the dog what it means.