Okay, as we have just hit 100 notes on this, let's talk.
Rit DyeMore dye for synthetic fabrics does not work like regular Rit dye. Standard Rit may not give us the brightest or longest-lasting colors, but it is popular because it's relatively easy to use in a variety of different applications. You can dye on a stove, or in a bucket or a sink. You can tie dye it and process that by leaving it in a trash bag in the sun. If you hate your roommates, you can even dye fabric in your washing machine. You will generally get a decent result with any of these, because natural fibers are able to hold onto pigments.
Rit DyeMore is popular because it's literally the only easily-available product that can even remotely attempt to perform the near-impossibly task of dyeing polyester fabric. It's popular because basically nothing else will do what it does. It's also popular because people are familiar with how easy Rit classic dye is and they think that using DyeMore will be the exact same process.
This is not true. This is not true because honestly we shouldn't be able to dye polyester at all anyway. You may say but hey, Dollar-chan, I see brightly colored polyester fabrics all the time! They're bright and cheerful and they don't fade when you wash them. And that's because a lot of polyester fabric isn't dyed. This comes down to the fact that polyester is plastic. It's great plastic, but it's plastic. It's plastic the same way this thing is plastic:
[image description: yellow and red Little Tykes Cozy Coupe children's foot-propelled car]
This thing is not dyed. They start out with red and yellow plastic pellets, and then melt and form those plastic pellets into the shape that they want. Polyester fabric is the same thing, except that the shape that we want is for it to be thin hair-like strings that can be turned into cloth. The easiest way to get red or yellow polyester fabric is going to be to start with red or yellow polyester plastic pellets, and then turn them into polyester fibers for polyester cloth.
If I wanted to make an orange Cozy Coupe, I could mix the yellow and the red pellets together, and then when they're melted, the colors would mix and I'd get orange. If I want to make orange polyester fabric, I can mix yellow and red pellets together and get orange polyester fibers. The important thing about this process is that the pigment isn't transferring on its own. We're not moving a pigment onto the fibers. We're mixing plastics and then reforming them. If you want to keep your plastic in the state it's currently in (coupe or fabric, your choice) and just change the color without changing what it is, you have a different situation.
It is extremely difficult to change the color of polyester plastic once it's made. That's actually one of its big advantages. The color's in the plastic, so it won't fade when it's washed or exposed to the sun. It just won't come off. That's very cool. When humanity is long gone, your XL Twin bedsheets you got conned into buying in 2009 will still be bright green and purple in the landfill.
But it comes with some limitations. One of those is that, if you want to change the color of polyester plastic, you're going to have to play by its own rules. There isn't really very much wiggle room out there for how the procedure should work. Actually, it's kind of amazing that there is a possible stovetop dye procedure for polyester dye. As anyone who does sublimation on polyester knows, which is a thing that I'm sure everyone has done, you set the heat press for 350-400F for sublimation. We can't set our stove to 350F because water boils at roughly 200F. Once the water is boiling, it stops getting hotter, so if your water is boiling at 212f then you're never going to have a dye bath at 350F, so you'll never be able to dye the fabric at the same temp that you sublimate it.
Rit DyeMore allows us to do the impossible. To get polyester dye to accept a pigment at a temperature under the boiling point of water, a lot of what we'll call Spooky Yucky Chemicals have to be used. One of the reasons why its so important to read the DyeMore instructions is that you really do not want to accidentally ingest this product. You don't want to get it on places that you don't want to get it. I don't know what's in it but I've never eaten any of it and I'm not dead, so that all sounds solid to me.
You're violating the very laws of nature by attempting to dye polyester at all. This process does not want to work. Back as recently as 2010, home dye of polyester fabrics was not actually considered possible. This means that, if you want this to work and have any kind of long lasting results, you better read the instructions, do what they say, use your "please" and "thank you"s. Tell the dye you appreciate it. Give it everything it asks for and maybe it'll actually do what it told you it would do, because it's looking for any reason at all to make the process fail.
So no, unfortunately, you can't tie dye with Dyemore. You can't sponge dye, ombre dye might look very weird. You're already right on the edge of breaking the laws of physics. Just be grateful that it works at all.
[text on image: Nobody claim rit dyemore as "your dye". We're all going to walkin real slow. Be good. Be quiet. Be cautious and respectful. Don't touch anything.]