Yeah, unfortunately they are not easy to spear, well they are very easy to spear if you can find one!
Two main varieties, the Red and the Tub with the Red being the most common.
Of course like all the other fish nowadays, they are not really common at all!
Anyway around my way, Gurnards are generally found in deeper water, 50' +.
They are very prized by shore anglers because very few are caught close to shore, the guys call them 'Carrots' where I live.
We catch them from the boat over gravel bottoms, we prefer to use shellfish for bait but they are scavengers so will eat virtually anything.
One point of note is just how vocal a gurnard can be, they make a croaking sound when under stress, for some folk the noise, really can be quite disturbing!
For average size Reds of around 1.5lb I boneless fillet them like I would do to a mackerel but, I then skin the fillets.
Crispy fried Gurnard, in a white bread sandwich with lashings of salted Guernsey butter has long been a family favourite