These are some of the writing implements I thought I could use. As long as it won't run or wash out, I will use it.
The first thing I did was draw lines with a black marker on the paper side of freezer paper.
Then I ironed the waxy side to the back of the fabric. This is to stabilize the fabric for writing. For the best adhesion, I recommend that you iron both sides with a hot dry iron.
Then using a light box or daylight window, I could see my lines to write. If you don't care about the straightness of your words, you don't need the marked line, but you still need the freezer paper.
So I started testing my pens. I thought I would like a metallic gold. No. Black? No. Green? No. Thinner black? No. Brown? No. I tried so many different thicknesses and colors. Either I couldn't discern the words or they were too much like blobs or they were too obvious and in your face. I didn't like anything.
I finally realized that it wasn't the pens and the colors.....it was the fabric. Even though I looked at the fabric as a tone on tone, it was just too busy with too much contrast. I switched to a less busy fabric and I found a pen to work. It was a good balance.