I want the Wall Builder skill for the Paradox Brothers. However, I don't know how to get it. Do I use Paradox Brothers to farm, or should I be farming Paradox Brothers?
Use the character that you want the skill for in PVP or LDs. PVP has a somewhat higher chance of getting drop skills(maybe about 25% higher?) so you could use it there and gamble for a drop.
I recommend just play pvp with a normal deck (non-farm) using P bros character.
Personally, I noticed PVP has way better drop rate for skills rather than farming LD with farm/non-farm decks.
To get a drop skill you should use the character you want to get the skill to duel at PvP or farming LD at gate. So, in this case, you can just keep dueling using Paradox Bro and you'll eventually get the Wall Builder skill.
Use the P brothers at pvp/legendary duelists, it was a bit of a grind for me