Due to me not being careful my bike cleaning brushes all now now covered in a layer of grease and oil that makes them useless for cleaning anywhere other than the drivetrain. They smear oil over the paintwork and Ive resorted to just using rags.
Ive tried soaking them in de-greaser but this makes no difference.

Any suggestions on how best to get them clean again?
Ta.

White spirit/petrol/meths/paraffin – or pretty much any solvent

Don't let your drivetrain get so gunked up in the first place. My brushes come clean with a rinse after using them with Hope Sh1t Shifter on the bike.

Suggest you clean your drivetrain with something like white spirit and then buy some new brushes.

If I wash my hack/commuter bike drivetrain it gets my brush really gunky with thick black greasy gunge, so I make sure that the next thing I wash will be an MTB plastered in mud. If it was fairly clean it'll just leave gunk everywhere, but the mud helps bring it off when just washed with a bucket of hot soapy water. The brush is then clean enough to use for more delicate paintwork …

White spirit and a rag. Then methylated spirits and a rag and allow to dry.

Thanks for info – I now have nice clean brushes thanks to some B+Q paintbrush cleaner. Worked a treat. Stumpyjon – the gunked up brushes originally got that way from attempting to clean up my commuter bike. Cheers all