If they will not give you permission to take their motor to bits,
then you are not going to be able to deal with each magnet separately.
You cannot do this to all the magnets while they are in the assembly.
It may very well assist the process to heat the magnet under attention
but i don't think it is necessary.
As 'Dean Huster' has already said ... "this project requires enough
amperes to make normal wiring melt",
and he is quite correct of course,
however i think that fortunately the current only needs to be present
for a short time, thats why its called 'zapping'
You will not get the sort of current you want unless you put several
motor car batteries in parallel. You would need some serious form of
conductor, and each extra turn you add will increase the your burst
of magnetic field.
On the down side ...
As 'Glyph' has said, the material used by the manufacturers will have
been chosen to suit their intentions, and it will almost certainly
already be magnetised to saturation, or near saturation.
You could possibly purchase replacement magnets of higher strength,
but this brings other problems with back emf and so forth.
One possibility is that you could increase the cooling somehow, and
simply push the motor harder by overdriving it a bit.
Again, if you cannot take it to bits, then you cannot deal with the
magnets on an individual basis.
And if you are willing to lose some top speed,
in exchange for some higher torque,
Then altering the gearing, might be easier than tweaking the magnets.
Best of luck with it, John