To answer your original question, I’ve used this previously: Epson Value Photo Paper Glossy, https://www.amazon.com/dp/B01BHL3052/ref=cm_sw_r_cp_api_i_OynxFbAE2214K

Toner transfer is good with that paper, but after you get the paper backing off there’s often a clear residue where toner wasn’t printed that you have to be super careful about scraping. Another user here has a great YouTube video and he recommends a soft tooth brush. FWIW, I found that my acid etch (copper sulfate, pH 1-3) was able to eat through little bits of residue anyway. I’m going to try the yellow toner transfer paper you linked next, because I’ve heard it’s better to work with.

My additional two cents:

For a good toner transfer and etch, you need to 1) transfer the toner and 2) get the backing paper and excess non-printed regions off the metal without disrupting the toner

The success of your toner adhesion to the aluminum will depend on 1) your surface prep 2) the type of toner 3) how that specific toner responds to heat and pressure

I have a brother laser printer. For toner type, I found brother brand toner to work better than generic brand toner that I use for every day printing. I now keep a specific brother toner cartridge to swap in for printing toner transfers. I also found that adjusting printing settings made a BIG difference. I manually forced my printer to its heaviest vs. “normal” ink settings and printed with the generic vs. brother toner. I found the brand name toner on heavy to have a visually richer print which means more chance of successfully transferring that toner to the aluminum enclosure. I found the generic toner on heavy printing to start to blur some of the finer detail of my pedal art, but YMMV.

For surface prep, I’ve had better luck when sanding finer and using naphtha instead of acetone. You are essentially stamping softened plastic onto a metal surface. The finer and more even your sanding, the more microscopic contact points for the toner to stick to. I don’t quite go all the way to a mirror finish, but I go a few grits finer while wet sanding than most posts I’ve seen. If your toner isn’t sticking then your surface isn’t clean/flat enough and you are either heating too briefly or way too long. Contrary to some videos and articles, I’m going to guess you are heating way too long based on your post. Toner is made up of polymer (plastic) materials that have a glass transition, softening and melting temperature not unlike melting a jolly rancher or blowing glass for a vase. You just have to lower the viscosity (melt it) enough to transfer to the aluminum. Once you heat the toner enough to transfer, any additional heating time isn’t adding any additional benefit and could make things worse. Pre-heating the enclosure surface and having even, ample pressure during the transfer are key. I use a rolling pin or an old ceramic coffee cup to press evenly across the surface after heating for about a minute. You want to get the toner hot to transfer it, press it, and once it’s on the aluminum you want it to cool and set. Once I started preheating the enclosure and heating the paper while pressing for <2 minutes instead of 10+ mins I saw much better results from my particular setup. At first I used hot water to quench so that the paper backing would dissolve better, but I found lukewarm water and a longer wait time in water (10 mins) to be better for toner adhesion. Be careful with very cold water, a thermal shock could cause loss of adhesion between the metal and toner but I haven’t tested this behavior.

If you haven’t, please watch this video: https://youtu.be/CvPIM5ZFWXw

The success of your removal of the backing paper/non printed regions will be a function of 1) paper type and 2) removal technique

This is the part I’m still learning about and need more practice with. I described my issue with the glossy photo paper above which is why I’ll be trying the yellow PCB paper next. So far I think patience is probably the key factor above any physical variables. I found the light brushing toothbrush technique to work really well (better than fingers or toothpicks) but try to not go overboard while doing it. You want to touch the black toner regions as little as possible so that they are thick enough to withstand your etch. My least favorite etch so far came from spending way too much time trying to get every speck of backing paper off and taking too much toner with it. The resulting toner thickness was too thin and my etch ate right through it. So make sure to get a good balance there. Finally, be mindful of your etch time. The sodium hydroxide you are using is probably aggressive enough to attack your toner and/or the interface between your toner and aluminum metal effectively “cleaning it” for you which you don’t want in that case.

Another great suggestion I got from reading some other posts was to practice on aluminum flashing or the backs of pedal enclosures before doing your real print on your intended pedal. It’s more work, but you are able to dial in the process variables for your setup. I started with aluminum flashing to practice, but it was a lot thinner so heating was a bit different. You might have more luck practicing on enclosure backs (lids?) that you can always sand down again anyway.

I hope this helps! Please follow up once you start getting good at etching so you can teach us what you’ve learned in your own experience.