How you diy clean and with what products?
Need to use wet vacuum to finish the cleaning?
My cleaning regime is nearly as good as the so-called "chemical cleaning". We have 2 x FCUs switched on daily (thermostat isn't set v cold though) and our bills rarely cross the $150 mark even for the hot months with 33-35 deg C.

2 adults, 2 children. MIL comes over to stay on Fri-Sat so that'd be 5 pax.
The past month, my bill was $118, previously $115. Haven't factored in U-Save.
But have to mention that my BTO is the new ones, hence the walls do not get warm even with the morning sun shining on it. Same goes for the floor and ceiling. The full-height windows have somewhat thick curtains drawn during sleeping, so the loss via that is reduced too. And our thermo is only 25-26 when we are not asleep, 26-27 when we are asleep, sometimes 28 deg C even when it is cold. But then again, during weekends Friday night all the way to Sunday night, 1 unit is nearly 24/7.
So at least for me, aircon = $$$ is not true.
I use my Panasonic Oral Irrigator to spray the metal fins. Pls do not use those pressurised plastic containers that you use to water plants etc. There is a explosion risk if you over-pressurise.
And Jackie Aircon foam cleaner. NTUC Finest/Home Fix. I bought many cans during offer, S$8.80. Regular is 12.80. 1 can gives 4 cleanlings for 9000btu/hr size FCUs.
The centrifugal fan blades, I use a small paint brush, cloth and also aircon foam cleaner.