I have always been reluctant to stick my neck out on APUG - it usually results in getting your head cut off but I'll take the risk this time. I use Jobo 1510 tanks for 35mm and was a regular user of DDX for several years. 1+4 with a litre of DDX gives 5 litres of developer at 1+4. A jobo tank takes 240mls but call it 250 for ease of calculation. I simply poured 250 mls in and developed one film and after I had developed 20 films the DDX was finished. No waste at all

Every film came out fully and properly developed. I don't think I was just lucky