I have used, and still do now & again, Winsor & Newton #7 kolinsky sable brushes that I've had for years, because for a long time sable was the only decent choice.
But I find them a bit too soft. Synthetics have improved considerably, and my preferred choice now is -
Winsor & Newton Sceptre Gold 11. These are sable - synthetic mixture and have a performance that is very similar to all sable, but are very slightly springier and more resilient. They are also cheaper; it's not just the price, I actually prefer SG 11 to #7
They are available at The Range hobby & household stores, or Surf t'Net
Of course, the only way to find out is to try them for yourself
Examples of prices - Sceptre Gold 11 size 1 = £4-10 size 5 = £6-50
(approx) Kolinsky #7 size 1 = £10 size 5 = £34
For cleaning brushes, I routinely use white spirit or water, depending on the paint, and now & again clean them with Masters Brush Cleaning Soap. Surf t'Net for availability, and YouTube for its use