How nice that you've adopted two little ferals!
Exchanging bedding for a 10 days or so is a good start. I would put a drop of vanilla on the back of each kitten's neck...to give them the same odor. Now I would exchange rooms. I assume the two kittens sniff the doors where the other kitten is. That helps.
The next step would be to allow them to see each other, but have no physical contact. Some people prop one door open an inch, but make sure the kittens cannot get together. A hanging toy would be helpful so they can bat it and play together. One member used a screen, and that's also good, but they cannot conduct interactive play, unfortunately.
If this goes well, I would put one in a playpen or carrier and put the two in the same room, and watch the reaction. You could change which kitten is in the playpen. That is the last step before a face to face introduction. I would take my time with the whole procedure. Don't rush any step. You can judge by their reactions when it's time to move forward or go back a step. Of course, you'll want to monitor them when they are together.
Be patient. I think it's just a matter of time. They might not cuddle, but when they're kittens, it's more likely that they will.
Please keep us informed! And we do love pictures.