How to lvl up grenades for high levels
 

Well, how i leveled them up is:

1. Go to tormenta a healer would be nice.

2. Treasure room is good, there's also an advantage... you might have a chance of getting a legendary weapon!:12_1_138:

3. Oh and watch out... if you kill an enemy and they drop a loot pouch, loot chest, or loot skull chest, they might be far and you won't see your treasure. Watch out for that!:piratewheelgo2: