Renderotica

the only things currently that can collide with multiple figure in Daz is DForce, Fluidos and the old Dynamic Cloth. it is really annoying.

I got some help with this awhile ago on another project. I use it regularly when i have 2 figures on a bed or whatever.

I get my figures posed how I want them. Switching the item to be collided with between the figures. I select the items that are going to cause the collision. Then Go to Edit > Duplicate Nodes. If you're using a figure with a grafted figure you'll have to select the grafted figure too by holding CTRL. the duplicate Grafted figure will parent itself to the original figure simply use the "Fit To" to switch it to the Duplicate main figure. I strip all the Textures from the duplicates making them either Gray or White.

Then I export the Duplicates to Hexagon (Since it's free from Daz) or any mesh editor your comfortable with. Now Hexagon will revert all the figures to their base resolution. This isn't a problem. I remove all the surface domains and materials their not needed anyway. I then select all the Figures and weld them together making an new item. I delete any polygons that are unnecessary, Rename it and save it. Then I send it back to Daz. I'll usually add Sub-divisions in Daz if my original figures have high resolution. Then I set the collision modifier to my newly created item. Works pretty well for me.

There is a drawback though, If you make any adjustments to the original collision figures that affect the collision effect, you'll have to do the whole process again.