Starting my 55 g over.

[MamaLovesHerReefTank]

I have a 55 g that we had before our 125. Been sitting empty for quite a while. I want to start over completely fresh with it.
A few questions if anyone can help.
I am going to use muriatic acid on all the extra rock I have sitting around. What is the ratio of water and muriatic acid?
Once this is done, rinsed etc, can I put it right in the tank? I am going to do a natural cycle with a piece of shrimp as there is no hurry to set this up.
Sand has been sitting in a bucket for a few months. Can I just rinse well and reuse?

 

[SDReefer]

This video may be helpful with curing used live rock.
I've reused sand before and all I did was rinse it thoroughly.