Ygg seed & Berry can be pushed just as fast as each other, So no they don't have more spammability, The difference between the two is the weight, One weighs half of the other the one weighing the half is the seed, it restores half your hp/sp. berry is 2 seeds so double that weight. It fully restores. You can carry 200 seeds or 100 berrys, Seeds are usually for classes that don't drain out all their Hp/Sp in one shot. Berrys are usually for Champions, Ninjas with Final strike, stuff like that.
Glistening coat needs to be crafted with the materials. Look at the skill description for creating glistening coats. You need to farm those items for 1 G/C. There isn't a room to farm them.
Alot of people cheat to get them by AFK farming. -_-