With what do you have to wash the oil base brushes ?

Most people reach for white spirit. Pour small amount into clean empty mini tray or can then work brush from side to side for a minute. Leave to stand for 5 mins and repeat until all oil based paint is removed. Professional painters might use mineral spirits or turpentine. Make sure your wearing plastic gloves, and gently work the spirit between bristles, soak and repeat. If you leave it over night, this can work well, but risk damaging bristles. Good tip, always spend a bit extra money on your brushes, clean regularly, and store clean and dry, and they will last along time. Hope this helps.

You can use white spirit or a brush cleaning solution for solvent based paints 👌

White Spirit should work. Or you can buy a brush cleaner from most paint stores designed to clean oil based paint from brushes. Or alternatively don't use oil based paint. They are highly toxic and make cleaning a real chore. Good quality water based paints perform just as well these days.

White spirit

Use white spirit and on a empty bucket to get the brushes cleaned and ready for the next job

Use white spirit to clean brushes, to do this pour a small amount in a bucket or even a paint kettle, clean thoroughly. and leave to dry. Make sure to do this every time so that your brushes don't get ruined. Hope this helps.