Need to get better.

[Einion]

Should I grab some dedicated brush soap or carry on using cold water with a tiny tiny amount of fairy liquid?

Opinions vary on this. I certainly wouldn't bother as common handsoap can do the job just as well (for much less money needless to say) and may be better for your natural-hair brushes; shouldn't make any difference to the synthetics though.

In terms of maintenance of brushes on an ongoing basis, the biggest aid is to minimise the need to actually wash them by adopting a good rinsing habit - rinse thoroughly and often - and adopting a double-bath rinsing system will help a lot here with the thoroughness part. A little dishwashing liquid in your rinse water (first container only or both) can help too.

Einion

 

[Tommie Soule]

yeah i wash my brush well every 10 seconds at least and no soap for me! (again, not because it's not a good product)
And i treat them firm yet gentle.
My brushes last a good few years.

T