Over many years I have found wet towels to be the most effective and easiest way to keep the temp of your wash and beer down in the warmer months. The first 2-3 days are the most critical as your wash can easily create another 10 degrees above the ambient temperature, and your beer can easily add another 4-5 degrees. In both cases this can have dire results on your end product.
The best way to keep this temp down is to wrap one or two wet towels around your fermenter. Just wrap them around the outside and tuck the towel in like a sarong. You will need to keep it wet morning and night, especially in the first 2-3 days as mentioned above.
After a few days you can remove the towels as long as it is remaining under 30 degrees. If it creeps up then wrap the wet towels around again.
See ‘Why is temperature so important?’