When gluing most types of trim, including double welt, to furniture I generally use a white glue(such as a white wood glue) that dries clear. I use this on most fabrics when you are gluing the fabric to wood. If you are trying to glue double welt and to the finished rattan wood, I would suggest using rough sandpaper and sanding the finish (either sand the finish completely off or sand it enough to roughen the surface to give the glue something to stick to. It is hard for glue to stick to a smooth finished surface). You would fold the sandpaper in half and only us the folded edge so that you can only sand a thing strip that would be under the double welt. However, before doing this, test it on some rattan that is hidden and won't show to see if it works.
If this doesn't work for you, another method I use is to use (with or without the glue) spray paint to paint the tops of the staples the same color as the fabric. After the paint on the staples has dried, I put those staples into my staple gun and put the staples right at the center seam and staple it into the wood. Sometimes I only use the staples at stress points, such as at the corners. If needed, at times, I have stapled the entire double welt trim to the wood.
Best Wishes,