So here is a short breakdown of how I magnetized the missile pods for my Voidraven. For this I needed to buy an additional missile bay set, but I'm able to take them off without leaving any visible traits on the model itself.
For the missile pods I took four strong large magnets and placed them on the inside of both the missile pod and the flyer itself.
I drilled small holes in the back of the Voidlances and placed small magnets in them.
On the back of the Voidlance slots I placed two larger magnets. I did not find it necessary to drill holes for this.
And there you have it hope this helps.
Kabal of the Forsaken Masquerade
Coven of the Flayed Man