For metal and cast iron grill grates, coat lightly with a high temperature oil like Canola or Peanut oil – wipe off any excessive oil, install the grates and fire up the grill. Heat the grill on high and let it burn for ~30 mins. This will burn all the solvents and impurities off of the heating elements, grill grates, etc. Note that porcelain grates won’t need a coat of oil, but will benefit from the burn in process to remove any chemicals/impurities that were applied by the manufacturer.
Now it’s time for propane flames to meet with forged cold steel. Turn up the heat and sit back while you watch the griddle plate blacken. The griddle will billow with smoke. That’s called “smoke point” and it takes about 30 minutes for your Blackstone to get there. So relax, grab a seat, and watch the smoke fly by. When all the smoke’s gone, you can turn off the griddle.
Clean the exterior of the grill. Soapy water is the safest cleaning solution for most gas grills. Just make a cleaning solution with water and a squirt or two of mild dishwashing soap. Wipe the exterior of the grill with the soapy water, use a rag dipped in clean water to remove the soap residue, and then dry the exterior of the grill thoroughly.