Praying from the heart simply means praying with feeling...whatever your goal, you have to really want it and send that desire to Spirit. The words you use, whether commanding or hopeful, are up to you. When I do cursing work, I shout out my command as I want it to happen, and curse my target with venom, hate, profanity and anything else that comes from my righteous anger when I am doing the work. Put all of your feelings into the work and whatever comes from you will be authentic and "from your heart".
Your detailed questions about laying powders are answered in these pages, or you could book a magical coaching session with someone from AIRR, who would be happy to guide you through the process. www.readersandrootworkers.org/