I use a 1 quart plastic measuring cup similar to Richard. (I think I got it Walmart or Target someplace like that). I take a 5 gal bucket with some water and add my chems to that. That way when pour the bucket into the pool, I have some control over how fast I'm adding stuff. Just place the whole bucket into the pool, then tip it to slowly pour out the contents in front of my deep end return.
I was a little worried about using plastic when adding acid too. But, the cup didn't melt or anything, it worked a champ. I have one of those OXO ones you can read from the side or from the top, that way I can keep the cup low and still read it like Richard said. I'm not a big fan of glass by the pool. I had a pyrex measuring cup for awhile, but just got nervous I would break it and get glass in the pool. I'm not fan of any glass by the pool frankly.