I discovered something. When you start explaining what crash cymbals are, most students only think about the crash cymbals that you hit with a stick, and not the orchestral pairs that you strike together. What's even more interesting is handing a new student a set of crash cymbals, and listening to the result. It's usually not pleasant. Cymbals are very hard to play. They take a lot of practice, but practicing cymbal crashes is very tiring. They are heavy. The heaviness is one of the problems that I find with most school music programs. Most band directors tend to purchase crash cymbals that are too big and/or too heavy for the students that will have to play them. Consequently, they never develop good technique, because they are constantly fighting the size and weight of the cymbals. It's better to have lighter and smaller cymbals, and then work your way up for really big crashes. I know that in most school situations, there is only going to be one set of crash cymbals, due to budget constraints. However, I would try to find a way to purchase at least two pairs of crashes in different sizes and weights. It will give you sound options, and make developing good technique easier.
I like to start students out using a method that is similar to a certain method of teaching skiing. In the snow skiing world, it's called the Graduated Length Method. In this method, you start with short skis, and when you become proficient with those skis, you gradually increase the length of the skis. You do this slowly, so that you become accustomed to using proper technique with each length. The first set of skis are not much longer than a pair of ice skates. With cymbals I'll call it the Graduated Size Method. I start students out with a very thin and light set of 15" or 16" cymbals. Once they get the feel of throwing crashes, I move them up in size and weight, eventually ending up with some medium weight 20 inch plates, that were former Bosporus Medium Ride cymbals. They are fairly heavy, but manageable once you have good technique. Cymbal thickness plays a large part in your technique too. Thicker, or Germanic style cymbals, need a different technique than very thin French style cymbals, regardless of size. Viennese style cymbals are half way in between. I like the even sizes myself, and I know a lot of players that like the odd sizes. It's all personal preference. Frank Epstein of the Boston Symphony had a legendary set of 20" French crash cymbals, and when I was with the United States Air Force Band, we had a real nice pair of Viennese 19" plates that were the "go to" crash cymbals for 80% of our cymbal work. Our plates were by Advedis Zidljian, K Zildjian, and Sabian.
My personal crash cymbals are recycled drum set crash cymbals that were made by the now defunct Bosporus Cymbal Company in Istanbul, Turkey. They have a nice dark sound with a lot of spread. They work for most applications. My largest crashes are 20" recycled Bosphorus Medium Ride Cymbals. They are a little thinner than most contemporary medium ride cymbals,slightly heavier than the old time crash/ride cymbals. They work great for big dramatic crashes. I've used Zildjian and Sabian crash cymbals, and they are wonderful too. I've never tried the Paiste Orchestra cymbals, but I'm going to order a pair once I get some more money, so that I can try them out. I'm sure the "purists" will hate them, but I'm interested in exploring some new sounds. I tend to like to think outside of the box. I have heard from some folks, that they are great. At the same time, I've heard, " yes, they are great, but don't tell anybody or quote me." In an other words, Zildjian or Sabian are the only "correct" gig in town. My belief it that what is involved is endorsement money, or endorsement money for someone that they know. Money talks.
Orchestral crash cymbals should be held by leather straps and not by wooden handles. Leather straps come two ways: those that you tie yourself, and those that use ball bearings to keep the strap from sliding through the hole in the cymbal. I've used both, and they are both good. Currently, I'm using the ball bearing ones, because they are more convenient. I don't think that they would work as well with a particularly large set of cymbals. Tying a cymbal knot is not difficult. Once you are shown how, you will remember how to do it. For large cymbals, you will want to double the knot.
Cymbal technique is a subjective subject. There are several ways of playing crashes, and as long as the method that you use works, use it. Here's my method: Hold the cymbals upright in front of you, touching each other. Angle them to the left at about a 20 degree angle. Slide the top cymbal down about two to three inches. Pull them apart and angle the top cymbal down at about a 10 degree angle. Bring the top cymbal down in contact with the bottom cymbal, while at the same time you push the bottom cymbal up against the top cymbal, contacting the top cymbal at the top first, and then the bottom part of the cymbal. This will produce a nice flam effect, which is what you want. It's uneven contact and multiple contact. Think of the word "crash." For larger cymbals it would be "curr ashhh." You'll have to experiment with just the right angle and contact position, in order to get a nice full sound without an air pocket "woof." Eventually, you'll get it, but it's going to take a lot of practice. In addition, every set of cymbals, every size, every thickness, is going to involve minor adjustments in order to produce a good sound. Good luck.