I use a Dremel 8200
and it works fine on plastic, resin and metal.
Make sure you have a variable speed model and set it on the lowest speed, use a sharp drill (I use HSS bits) as blunt ones will cause more friction and therefore make melting the plastic more of a risk.
High speed cutter bits like this one
are useful for enlarging holes and heavy duty shaping as long as you remember to reduce the drill speed. I tend not to use cutting wheels or sanding disks as these have a high risk of melting plastics due to the friction caused in the way they are used.
Also... If you do need any more advice then the link I initially posted has loads of information - plus I am the author and have a bit of a magnet addiction... More examples of how magnets can be used can be found in my other magnetising threads here: AM
and here: DA