OK Sacred, here is few words for your questions, In the first days of Orgonite, probably 2000 or 2001, Don Croft (the Orgonite guru) said to get any shavings that you can, dirty or not will not make a difference, he was saying to remove the old cigarette butts from the shaving, but you really did not have to do that if you did not want to, so worry not about the dirt, it may even add something to the mix.
You will make good looking Orgonite if you decide to have a business and sell it, otherwise you do not need to have it all prettied up If you need to make your Orgonite look good, first, it does not need to be a good looking piece to gift in nature, actually the worst it look the better, only if you will have that piece shown in your home or giving it to someone.
So if your Orgonite is rough looking, do as Stephen said “double dip”!!!, make a small batch of resin with nothing in it, and put your piece in it and remove it, or brush it on, it should give you a fine finish As far as shells, put as many as you can in the Orgonite, it creates a good spin
Good luck my dear (check your PM) Josh