I wish someone said this to me before I went down this rabbit hole.
Only buy painted 2nd hand models if:
1) You like the paint job, position, etc.
2) You are looking for spare parts to kit bash.
3) You don't care how they look, you just need them to be on the board.
4) They are metal.
The amount of time and materials you spend on recovering them is only worth it, if you have alot of spare time. You are going to loose detail, most of the loss is not noticeable though and well, mistakes happen.
Simple green is the most effective thing I've found in removing paint from GW's plastic minis (You can find it at Bunnings). That said, it doesn't remove it as well as you hope it will. It will also not remove some forms of undercoat, don't ask me what types, as I bought them second hand, it wouldn't remove it even after a week of soaking.
It has no effect on Plastic glues, never tried it on superglue.
With metal mini's you can use harsher chemicals to remove the paint, which would also take care of the glue.
On to your question.
Was it Super Glue (stuff you buy from Woolies) or Plastic glue (current GW glue or the blue Revell bottles from Hobbyco).
Superglue - If it is a clump of something, then it is most likely this one.
I have not used simple green to remove this type of glue, so it might make the job easier. I would give it a go as it doesn't hurt the plastic.
pop it in the freezer, it will make the bond weaker and easier to remove the parts. Then you can use Acetone (nail polish remover, check the contents, you want a low concentration 30%, high concenrations will damage the model) to remove the glue clump. Hobby knife is the last restort.
Plastic Glue
When used in small/reasonable amounts it does not take much force to break on infantry and is generally a clean break, when waaaay to much has been used, the plastic is basically fused, the plastic will break before the bond will, so arms will snap if you try to force it.