The only tools you need are:a dental pick,a bucket of clean water,small,sharp scissors(like embroidery scissors),and the most important of all is patience.
First of all,I really try to clean them the day I find them. It can become an overwhelming job if you wait until you get home from vacation.By then,they stink to the high-Heavens,and you want absolutely nothing to do with them.And,so,they will sit in the garage until your neighbors are convinced you're hiding a dead body.And you definitely don't want the police at your door,asking to search your garage.Just to find old,smelly sea urchins.Ewwww....how embarrassing would that be?
I've also found they tend to break more easily the longer they sit.
So,let's get to it,shall we?As soon as I return from the beach,I put them to soak in clean,fresh water.I leave the animal inside until all the spines are off.I've found that seems to give it more support.Or, I just may be lucky........whatever it is,it works.Cradling(gently) the urchin in my palm,I just start rubbing the spines off with my thumb and forefinger.Occassionally,the urchin will go back into the fresh water,if for no other reason,than I can't take it anymore(break time!).The fresh water,also,seems to soften the animal,so it's easier to remove,later on.
You may have to pull a few of the stubborn spines off,but just say a little prayer,grit your teeth,and tug ever so gently. If you can do it under running water(remember it's your water bill...)it seems to go much faster,but in these times of water restrictions,probably not a good idea.
After all the spines are off,it's time for the really delicate part.Getting that dead,stinky,critter out.This is where you need to go s--l--o--w.....
First,I run the dental pick around to see how lose it is.If you're lucky(and remember it is better to be lucky than good!),the animal will be soft and pull right out,but if not and if it's still hard,I take the tiny scissors and try to cut him up,and then remove it in pieces.
Just take your time,and PATIENCE!!!!
After all the spines are off,and the animal is removed,I soak them in a 50-50(or even weaker) bleach water solution for about 10 minutes.No longer.Then rinse really well under running water,inside and out.
I try not to dry them in the sun,as that seems to fade them.I just lay them on a cookie sheet covered with newspapers,and let them air dry.If you have a rack of some sort(a baking rack?) and a small fan,even better.
After they are totally dried out,I coat them with a 50-50 white glue and water solution.Inside and out.You can use either a sponge brush or an old paintbrush.They're like sand dollars.The more coats of the glue solution you apply,the stronger they are.
So,there you have it.That's how I do it.If anyone has another way,I'd love to hear it.I'm all about easier......
And that's why I always say,"If I pick up another sea urchin,someone please shoot me!"
But I always pick 'em up..........
(Note-once,I didn't have any bleach with me,and I used a touch of Dawn dish soap.That seemed to work too.)