Buying property
One thing you can do to see a greater range of properties, or to find the right property faster is to tell everyone you can, not just go to estate agents and look at newspaper ads (not that you should not do these!).
You may need to look for property for long term lease, rather than buying a freehold for tax reasons. There is a 100% tax on foreign purchases of property. There are a number of ways of avoiding this including long term leases and setting up a Sri Lankan company to buy the property (this requires a minimum investment and business use). Please get professional advice on this issue.
As always, the people who know best what is going on are the locals. You are likely to find that tuk-tuk drivers, shopkeepers and others who are part of the day to day functioning of the community often know best what is going on.
It is common practice in Sri Lanka for the seller to pay a commission to (almost) anyone who introduces a buyer. This may inflate the price a little, but the commission paid is likely to be lower than that paid to a proper estate agent. The seller can have problems if the buyer is shown the same property by different people!