Hairy dForce problems...
I'm having trouble with some hairs for Genesis 9. For example, the ones from MagicBrush. Although they're labeled as dForce, when I run the simulation to adjust the hair around the ears or an arm or just place it on the chest or back, absolutely nothing happens. Unfortunately, products like dForce Fluffy Twin Ponytails Hair also don’t have any attachment points that would allow you to manually bend the braids, for example. Am I missing some trick here?

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Strandbased hair (dForce hair) has default some setting that makes it rigid. Why it is done so I don't know.
In the surface settings try to lower Local Shape Constrain Stiffness, and it will become more dynamic. Other parameters can change dynamic as well, but this one is in my experience the most significant, Just don't go very low, it can cause the hair to behave weirdly.
The twin ponytails https://www.daz3d.com/dforce-fluffy-twin-ponytails-hair-for-genesis-9
I don't have it. There is some movement morphs, but if they don't work as you would like, you can try to above setting.
Alternatively you can make you own morphs, with geometry sculptur if you are Premier member, or with a 3d modeller.
As for the draping issue, because the vendor just kept the default constraint value on the hair without any tweaking... so the hair doesn't drape much so as to preserve the shape. You can go to Surfaces pane, select a surface, filter by Constraint, you'll find a property named as Local Shape Constraint Stiffness, its default value is 0.9, lower the value properly, then test a simulation.
Then I don't understand what you mean by "attachment points"... but if you mean custom bones to move the tails on https://www.daz3d.com/dforce-fluffy-twin-ponytails-hair-for-genesis-9 no there's no custom bones on the hair because it's a strand-based hair (SBH)... custom bones + weight mapping don't work on SBHs.
But the vendor can add morphs to SBHs, so you can find morphs like Blow....sth. on the hair in Parameters pane. Magic Brush usually added Blow morphs to the SBHs they made ~~
Thanks for the help! Yes, I meant "bones" like the one justed in G9's hand. For some hairs there are bones like "Left Ponytail", you can bend and move. Unlike other hairs the three Local Shape Constraint options are not present in MB's product. :-(
And you are looking at the hair and not the scalp?
Yes.
What shader does it use?
You can select the ponytail hair node, go to Surfaces pane, select a suface, in the upper left corner of Surfaces pane, there's a "Shader: ...", is it OmniHair or Iray Uber ?
My understanding is you can still ultimately run transfer utility on curves/polylines with the option of selecting either rigid or non-rigid for the weight transfer. Rigid will apply weights for the whole strand based on the root weight. Non-Rigid will apply individual weight to each vertex of the curve. In either of those cases the curves can be transferred onto a rigged proxy mesh rather than onto the G9 scalp (and the proxy mesh can have custom bones), but only in the latter case of non-rigid weighting would this be useful in most applications, such as ponytails etc. Of course, a non-PA creator would not be able to generate quote-unquote dForce SBH but I suspect the transfer and rigging with custom bones and custom-weight would still work on standard non-SBH curves.
It is Iray Uber (MDL).
Actually, as far as I experiment, I could create custom bones as well as face groups on SBH, fill general weight on selected vertices, and assign to face group binded with custom bones, however, I have no way to accurately edit the weight by using paint brush because the weight on polylines are toally invisible... let alone smoothing ~~
Though custom bones do move SBHs... its performance is very much lower than using morphs. So it's almost useless to me ~ While on the other hand, I can easily deform SBHs by using dFormer, Geometry Sculptor or Blender and create morphs. Besides, personally I've never seen custom bones on SBHs made by PAs, so I totally gave up using custom bones on SBHs ~~
I don't know if there's any good tricks for this subject matter... or any more advice from you PAs ?
I've also seen there're lots of texture maps of Base Color, Translucency, Glossy, Top Coat, etc. in the file list on this product's wiki page. So, I'm afraid this is not an SBH but a polygonal hair.
If you press Alt Shift + G to activate Geometry Editor, and can see hair mesh rather than polylines, it means it's a polygonal hair. Then you can freely create custom bones + weights to rotate the tails as needed... though that'll require more time and effort.
You will have freedom to edit the bones and weights of the proxy mesh. Any weights transferred from a proxy mesh to the curves will at that point not be accurately editable/visible as you have noted. As to any further advice, I do not have any I'm afraid.
Will have more experiment then ~~ Thank you !