Best Medium for thining GW Washes - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

I'm looking to thin a GW Wash Drakenhof Nightshade by about 50% and I know that at that level water will not give a great result. Can anyone recommend a good thinner. I currently have: GW Lahmian Medium Vallejo Airbrush Flow Improver Vallejo Matt Medium Vallejo Thinner Medium Liquitex Airbrush Me

Help with painting white helmets? - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

Initial Contrast Experiments (from us all) - Page 4 - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

Painting Imperial Fists/ochre yellow armour - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

Solved: Darken metal after the fact: shade or thinned black? - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

New painter having trouble shading/washing brightly-colored Space Marines - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

Initial Contrast Experiments (from us all) - Page 6 - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

Leaving the comfort zone of Citadel (GW) paints - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

New to weathering - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword

Washes for white power armor. - + GENERAL PCA QUESTIONS + - The Bolter and Chainsword