Yeah, closing the Manix2 is harder than the PM2. Grip strength and practice are all I can recommend. I grip the handle with all my fingers (not covering the slot) with the butt/pommel nestled in the the palm. This gives you the leverage to reach forward with thumb and index finger to pull rearwards on the locking nubs. Then you can whip your wrist to get the blade to seat, or just reach forward with the thumb to pull it in.
edit: when you've got the nubs pulled back, you have to give it a little shake shift the blade a little.
edit: when you've got the nubs pulled back, you have to give it a little shake shift the blade a little.