You don't need "19 sharp nails" - just go for a ride on pretty much any Greek track or path. I lost count of the number of big thorns that I pulled out of my tyres over a seven week period. A lot of the thorns don't stay in the tyre, of course. All you get is a very slight air loss and that little bead of sealant. I use 60ml of Stan's per wheel.
Don't bother with slime tubes, I've tried them under the same conditions and they're crap by comparison (ie, they still punture and go flat..)
The smaller thorns are still in the tyres, over that seven week period I didn't have one flat, whereas with tubes I'd have been repairing punctures every five minutes (or it feels like it anyway).
The other benefit is that you can run lower pressures with no fear of snakebite punctures.