Keep moving. My rule of thumb is that after the droid says you've found something "significant" and it's trash - keep moving along. That area is depleted.
As a general rule of thumb, i found that moving around more is better than less.
Blue mark II droid buffs help. use them.
With the above i got full dread seed in about 4 hours total of searching. With about 2.5 hours of that on Tatooine due to competition. (someone else would find it first)