Its my simple four step method
1) Clean ur dash board with simple dry cloth first
2) Mix Rs 5/- surf in 250ml petrol & thorughly apply on interior. Leave it for 10 minutes
3) Again thoroughly wipe with clean cloth dipped in clean pertol
4) Then apply dashboard spray and wipe with clean cloth well.
(Note: Dont use this pertol formula on transparent parts e.g. speedomater glass of deck display etc)