Bounty Hunter missions are short tasks of finding hidden characters. In order to begin a mission, you have to first complete Castle of Doom and then talk with Jabba in his room on the Separatist ship [M2.5]. At the beginning not all missions will be available. They will unlock as you progress in the story and unlock more characters.
Right after beginning the mission, choose Robonino and use the panel on the left . That way you will unlock a narrow passage which you can go through with a small character .
On the other side there's a long balcony , the droid is on its other side .
Yoda can be found in the northern part of the canyon . It's hidden right behind the tank found there .
Choose Helios-3D and keep going forward until a room with two corridors . Choose the left one and you will discover a panel .
Use it to open a door leading to a club . Padme is in the upper left corner of the room .
As Jango Fett, keep going straight until you reach a train hangar . Fly to the platform in the north .
Use the panel there as the IG-86 droid . Afterwards return to the south and keep going left. above there will be another platform with a panel .
Fly there, push the button and activate the panel . Now go maximally to the east and then south. That way you will reach the hidden character .
As the level begins, build a crane from the bricks in front of you , and go down the line .
Once you're down, change to Jango Fett or Cad Bane and fly over the pit on the left (before the fire) . Captain Rex will be in the north .
At the very beginning, fly left and use the booster . On the lower level you should see a red landing pad .
Land on it  and head to the south-east corner of the location. There you will find the fighting Plo Koon .
From the start of the level, fly maximally to the right . You will find a big burning ship there .
Fly round it from the east and a secret landing pad will appear at the top of the ship . Use it and go right of the gold toilets . The characters you're looking for will be standing there.
Fly west and then to the north . You have to land on the second landing pad you pass by .
On the left side of the location you will find a narrow orange passage . Use it as Robonino and go south. That way you will find Obi-Wan .