The little guide that attaches to the magazine is commonly called a "spoon", as it sort of looks like one.
Here are a few tips for using stripper clips:
1. I have a speedloader that really helps. You can buy one ("M16 Stripper Clip Speed Loader") from www.globaltactical.com for $16.95. This device attaches to the magazine. You drop the stripper clip into the shute, and them ram the rounds into the mag with a plunger. Works great, and much less chance of tearing the skin off your fingers with the GI spoon.
2. Clean off your stripper clips so that they are free of sand and debris. Use water or some other household cleaner, like 409. After you use your clips a few times, they will loosen up and work even easier. I tried using the used stripper clips for awhile, but I like the new ones you can get from Bushmaster much better. These are a little more expensive, but work much better. I have used some of mine more than 50 times, and they still work great.
3. If you are using the green (or black) GI magazine followers on your mags, they are tilting and binding when you are inserting the rounds on stripper clips. Switch to the Magpul anti-tilt followers that are the rage right now and you will notice a big difference in how easy the mags are to load.
Good luck.