Payment schedule when buying flat directly from HDB: http://www.hdb.gov.sg/cs/infoweb/residential/buying-a-flat/new/finance/costs-and-fees
Actually you can't just look solely at the purchase price of the flat. Don't forget to consider costs for stamp duty, legal fees, home protection fees, etc too.
Let's ignore those additional fees for now and say you only have to consider how to pay off the 190k. Based on your question, HDB will wipe out your CPF and grants; and the balance will have to be paid via cashier's order upon collection of keys, which is also when the loan starts. So let's say CPF and grants total 100k, you will have to pay the remaining 90k in cash.
Anyone pls correct me if I'm mistaken