Ditto ^^^^^ surgical spirit isn't necessary. Go easy on tea tree oil if it is an essential oil. I only put about 20 drops in 6.5 litres of mix, same with the citronella.
I make tea with 8 tea bags and 1 litre of boiling water.
Cup of vinegar
Squirt of washing up liquid
20 drops of oils
Top up to 5 -6 litres with water
Spray or sponge on.