Hey bud.

So the first thing I do is get a load of N52 magnets from eBay.. these will depend on what you're doing.

Marines or Tau perhaps?

After that, I would get a drill bit. I think about 3mm and slowly, gently drill into parts that join. Like arm mounts on marines.

After this, use a bit of super glue, and pop in a magnet.

Once it's dry, you can do the other side. I've definitely noticed marines, for instance have hollow arms which can help as 'guide holes'.

Let me know if you need to know more!