How to prepare a youma: In the case of Jadeite, you use a person. You visit them, and then knock them out. The youma will then take the appearance of the person and be ready to impersonate that person, and eventually attack. In the case of Nephrite, you take an object, endow it with energy. The youma will from that object gather the energy of it's victim, and eventually take life.
How to make a rainbow carrier monster (except Rita and Greg): For this you need the Black Crystal. The work is all done for you, it's just a matter of awakening their power. Once you find them, focus the energy of the crystal on their chest. The crystal will appear and they will turn into a monster. Just proceed with caution, and make sure the monster is on your side. Be prepared.

Morga (1)
Palm (2)
Flow (3)
Evil Trainers (not Youma) (4)
Derella/ (Mikan Shiratori/ Saffron)(7)
Murid/Dream Princess(11)
Titus (12)
Posessed Police Officers (13)
Tesni (14)
Petasos (15)
Widow/ Black Widow (16)
Cameran (17)
Jumeau (18)
Leo the Lion (19)
Ghosts/Spirits (not Youma) (20)
Gemini Twins (Castor [red] and Pollux [blue]) (21)
Possessed Naru/Possessed Molly; Possessed Princess Di/Possessed Princess Diamond (22)
Yasha (23)
Suzuran, Grape and Housenka (24)
Gesen / Game Machine Man (25)
Boxy / Bobo the Vulture (26)
Bunbo / Bumboo (27)
Bina / Veena (28)
Rikokeida / Techniclon (29)
Jiji / Pox (30)
Bakene (31)
Akan (32)
Mitsuami (36)
Shakokai / Polite Society (37)
Blizzard (38)
Misha and Janelyn/Janelle (39)
Lake Monster (40)
Papillon (42)
Oniwabandana / Ninjana (43)
DD Girls/ Doom and Gloom Girls (45)