So I've decided I want to learn how to sweep pick, and so I've started to try and learn the solo to `coffin' by black veil brides. My problem is when I try the sweeps I just sound like I'm strumming chord badly. So what is causing this, and where should start in order to be able to sweep well?
Best bet is to look up some videos on Youtube. There are plenty that explain how to get started with the technique. Chris Zoupa has a great video breaking it down. I just started as well and I can actually begin to see my speed pick up. Practice is key.
Sweep picking is hard to learn, and you will need to practice a lot.
I recommend you to watch videos on youtube that explain this technique. The best i know is Ben Eller, his guides are really good, he explains all from the start (+ I find him funny so his guitar lessons are not boring)
Part 1 :
Part 2 :

But remember that it will take some time until your sweep picking sound good.
Yes indeed sweeping is one of the hardest tecuniques to lesrn. I would start with 3 notes arpeggios, like the d major shape and d minor shape, they are the easiest ones.
Like all above said, practice is key here. Get a metronome, a simple exercise and only up the tempo if you're playing it flawlessly.

Here are some basic exercises I used. Start with a low tempo that you feel comfortable playing and up 5 BPMs when you're ready. Also check a couple of vids for technique.


These should be enough to keep you entertained for a long time!