Sorry, I don't know this plant, so can't suggest the best prop. methods.

You mixed in Miracle Grow what, (noun pls), soil or fertilizer? If you're trying for a 'soilless mix', then pls. leave out whatever Miracle Grow you added, it's defeating the point of the soilless mix.

If you're a newbie (am guessing so) when you follow what you read on a recipe like this, it's best not to improvise until you know more about mixes & growing in containers.

Actually, you can use a wide assortment of mediums to root cuttings, such as vermiculite OR perlite OR sand OR potting medium. With your plant, which loves a peaty potting mix, I'd use a regular (soil-less) potting mix, maybe with some perlite added for extra porosity. Stem cuttings can be made any time in the spring through summer. I really wouldn't attempt it now, if I were you.

Use cuttings of 4 inches or so, with all but a couple of the top leaves removed. I don't use rooting hormone, but lots of people do. Soak your propagating medium thoroughly, pre-drill holes with a sharpened pencil (or similar), insert the cutting and water again. Do not pack the soil down around the stem but let the water do the job.

I don't cover my cuttings, but a lot of people do. Use pencils or skewers inserted in the pot to support a plastic baggie or plastic wrap, but be sure you create some breathing holes in the plastic. Place the cuttings in a warm, location out of direct sunlight, and do not disturb except for watering. Do not be tempted to keep yanking on the cuttings 'to see' of they've taken root. After three for four weeks, gently tug on one to see if there is any resistance. Resistance means ROOTS!

Fertilization is not required when propagating. I'll recommend that you put any Miracle-Gro fertilizer away for the time being. Miracle-Gro potting medium might be what you meant, and some of those have fertilizer in them, don't they? (I don't use the stuff, so I don't know.) By the way, if Miracle-Gro is your soil-less medium of choice, be sure to add that extra perlite. (I never recommend vermiculite as an amendment because it collapses so rapidly.)

Rule of thumb is: keep it simple. There is absolutely NO need for a complicated, detailed recipe. All you need is something that will hold the cuttings in place and that will provide water AND oxygen to the cutting. I've had perfect success with all of the individual materials listed above. What I use depends upon the type of plant I'm propagating, the method, and what I happen to have on hand at the time.