actually, soft resetting and breeding will still take a TON of time and since you are in Soul Silver it would take far less time to learn how to RNG for a pokemon. Since you want a shiny, you will need to figure out what your secret ID number is, which is similar to your regular trainer ID except you can't see it. RNG seems really complicated at first, but in reality it isn't bad at all. All you need to do is find the seed you are looking for and you can get a Shiny
with any nature and any IV spread that you want. So not only can you have a dark
but you can have a really good one. Go ahead and google all of the info you need, smogon has some really helpful tutorials on how to do it. Also you will want to google a tutorial on how to find your secret ID without the use of an Action Replay device which is possible.
If you get started, and you have some questions with RNG feel free to PM me. But I do ask that you read
all of the info you can find first. The more you read on this the easier it becomes, also using a regular Nintendo DS is preferred for this.
If this process seems too complicated for what you are looking for, you can soft reset a ton. Though I warn you, you could reset a thousand times and never see a shiny charmander come from professor oak, when you could just spend a few hours reading and get it on the first few tries.