I would try using a 6-point wrench rather than a 12-point,(as pictured) to reduce slippage/stripping. Make sure its a mm wrench, not a standard U.S. Wrench!! (not good for high torqued bolts)
You can try using a pipe to slip over the wrench to slowly torque it off.
But you must be able to torque these bolts back on properly at the specified levels,or very close. the wrench that BRush recomended would be perfect. Eventhough its a 12-point, it would achive torque spec. before slipping. The primary reason for 12 point wrenches/sockets, is to fit in tighter spots, but use them carefully when losening very tight bolts!,
especially when used w/ a torque applied device i.e. torque wrench or pipe, were slippage can happen very easy.
If you plan on doing this kind of work on a regular basis you must buy a torque wrench & learn the spec. torque sequence,or very close.
A GOOD TORQUE WRENCH! not a twenty dollar one. And maybe even buy the wrench pictured.
I may have to get one of those for myself!!
Good luck!
'98 KDX 200-'91 KDX 250