This post isn't really a tutorial, but a jumping off point. I'm still learning how to solder and we don't really want the blind leading the blind! If you have any tips or know of resources, please post them in the comments!
I tried to teach myself how to solder several months ago, certain that it couldn't possibly be that hard. It's a handy skill to have. String cinches are almost impossible without it, and certain complicated bits and bobs become infinitely easier (and sturdier) when you can securely join two pieces of metal. I struggled mightily the last time I attempted it, but I needed a way to securely affix a glitter-sized piece of brass to a wire bit shank yesterday. I knew that soldering was the answer, and set about figuring things out.
The first stop was YouTube. I watched a few videos before I found The One. I've tried to embed it here for you to watch - if that doesn't work, you can go straight to YouTube.
The video did a great job explaining not only how to solder tiny things, but why. It clued me into my missing link - flux. The video explains it far better than I could, so I really encourage you to watch and then go pick up flux if you've been struggling. I found the brand he recommends in a 1.7 oz jar for around $2.50 at my local hardware store, and I'm not sure I'll ever use it up.
Here's my current set up:
The soldering iron is a Weller 40-Watt Soldering Station. I couldn't tell you whether or not this one is The Best One for what we need to do - if you're going to go out and buy one, I'd take the time to do some research and focus on sources that are involved in hobbies (esp. model trains and automobiles) or jewelry making. Having everything hot enough is really important (the video talks about this quite a bit), and depending on your materials this little soldering station might not get the job done. It's worked fine for me so far.
The little clamp thingies are called "helping hands" and I picked mine up for less than $5 at Hobby Lobby with the 40% off coupon. You can find them in the modelling aisle. They're great for keeping two pieces of metal together while you solder and they give you plenty of access from all angles. The base is heavy enough that it can double as a braiding anchor if you're gentle and put something non-slip under it!
I have silver solder that I picked up at Hobby Lobby - you can probably use other kinds, but I chose silver because I was concerned about the lead and fumes from rosin core solder. Under the solder is the flux - as mentioned above, this can be acquired cheaply and is an utter game changer. It holds things together, helps heat distribute, and helps direct the solder. Slightly blurry and in the foreground on the right is wire. I use 24 gauge wire that can be found in any hobby store's jewelry section for a lot of my bits and large buckles, but I also use 26 gauge for smaller models or more delicate bits.
Yesterday, after watching the video and making a 15 minute trip for flux, I succeeded in getting my brass glitter to stick to my wire shank.
I played around with some combination bridoon and curb shanks, too, and have thrown together a photo to help illustrate why this is such a big deal for me.
There's a quarter for scale, two of my previous methods for doing combination shanks, and then the neatly soldered shank. The first shank from the left is a single piece of wire carefully looped - there's a double thickness at the front of the bridoon, where it would sit against the corner of the horse's mouth. The middle shank is two pieces of wire - the curb shank and the bridoon, which has a tail near the mouthpiece that is carefully wrapped around the curb shank and pinched closed.
The old methods have some problems; the curb chain doesn't lie properly with the first, the second is fiddly to make (and the curb chain is still a struggle), and in both cases there's added bulk at the corners of the mouth. A soldered combination shank lets me determine the exact angle of the bridoon in relationship to the curb shank (they're rarely perfectly square in real life), eliminates bulk, and is in general neater and stronger than either of the other two methods. I'm pretty excited about this, guys.
Learning to solder also means that I can now close jump rings! Glory! String cinches are once again within my ability.
I hope this encourages you to try soldering - again or for the first time. It's a really fabulous skill to have in your arsenal at any scale!