Can someone recommend a clay for modifying small parts?

Is there any specific modeling clay I should go for if I want to try to modify a small part?

I have a general grievous model kit already build and came up with a cool pose utilizing one of the arms split with 2 lightsabers and another single arm with 1 lightsaber. Problem is, the hand for the single arm doesn’t hold a lighsaber, so I currently have the top half of the hand snapped onto the single arm. It works practically, and I’ve tried to angle him so you can’t really tell, but it’s still bugging the perfectionist in me.

If you really like the pose and want that to be it’s final pose then I’d say super glue it. Otherwise I’d say a small bit of sticky tack on the inside where it would be out of sight would be good cause I think most clays and stuff dry to be permanent

Sticky tack, blue tack, poster take or whatever it’s called where you live is a better option than clay. Some Clays can eat away at the plastic that us used for bandai model kits. If you want something permanent use a 2 part epoxy like Majic Sculpt or milliput.

Are you wanting it to be a static (non-posable) build, or do you want to be able to change poses?