Body Shop Rainforest moisture conditioner is well thought of, you could add oils to that or humectants like honey or aloe vera when the dews are suitable. Mayonnaise is pointless, it's usually polyunsaturated vegetable oils which do not penetrate.
I'm experimenting with the Body Shop cottonseed curl boost at present, it's very lightweight tho. If you can get gelatin you can make your own protein treatment or body art quality henna you could try henna glosses.
2a-2c, medium texture, porous/ colour treated. Three years CG, growing out mechanical and chemical damage = breakage and very high porosity. Past armpit length heading for waist.
Treatments: Komaza protein, Komaza Matani, coconut oil with sugar syrup. Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss ultimate volume
Styler: Umberto Giannini jelly, Boots curl creme, Rockin RInglets
Experimenting with: Mega-Tek, Curl Harmony reviver, Elvive Full Restore 5.