Just make a circle with your thumb and forefinger, and then overlap the finger with the thumb to reduce the size of the hole to the diameter of the barrel of your shotgun. Then hold the circle over the muzzle to act as a funnel, and poor the irish measure into the hole. If you do drop a piece of shot or two, what difference is that going to make? When you are shooting 40 % patterns or less at 30 yds, or beyond, your problem is not a missing pellet or two when you load ! Either powder measure works correctly if you do it right. You can screw up using an English measure too, and I have seen more than one man pouring shot right out of his English measure onto the ground.
When you are hunting with today's bag limits, there is no excuse to hurry the loading, and chancing losing the measure on that Irish measure. But, if that worries you, simply attach a thong of leather to the measure so it won't be lost if dropped, and attach the other end of the thong to your possibles bag or shoulder strap. Make it long enough so you can comfortable load your gun as you usually do. Always check your equipment before any shoot or hunt. Tighten screws, and replace frayed or worn out thongs. I almost lost a powder horn when my leather thong broke during a match. I was on a woods walk, and luckily felt the powder horn weight shift as it fell and was swinging from just one end still on my shoulder. The repair did not involve much work, but I should have caught it before the shoot.
