IIRC the connectors on the end of the hoses are often "Schrader" type; the same as found on car tyres (the smaller of hte two below). You can usually get a tool a bit like a hollow tube with a slot in it to unscrew them. If they are well crudded up then replace them or if less so then soak in white vinegar and a smear (tiny smear) of silicone grease.