I have no experience in house hunting in Singapore, but just like you I will probably have some at the end of this year since I am moving to Singapore next year.
From my own experence in flat hunting from my home country, four days is really a short period of time. I do think that it is possible though. The longer you have the more choice you will have.
My advice would be to prepare your agent very very well about what you are looking for and what facilities you require before coming to SIngapore. DOn“t take anything for granted. Describe in detail what is most important to you and what you can not stand in a house (like pink carpets)
Good luck!