VOA from Lok Ma Chau or Lo Wu stations

I have booked train from Shenzhen at 10.00 a.m. on Saturday 26 April. Before that I should travel from Hong Kong and get Visa on Arrival from Luohu (opens at 7.30 a.m.) or Lok Ma Chau (?) stations. According to the train company I should be in Shenzhen station 90 minutes before the departure. Is there any possibility to get VOA from Lok Ma Chau station? I heard that it is not so crowded as Lo Wu station. How long time I should reserve for the VOA application handling and immigration checking in Luohu or Lok Ma Chau? Could I apply for the VOA (at Luohu) already day before my train trip to China (only 3 days' trip)? I am from Finland.