Sub-q’s are administered to help rehydrate your rabbit and to help those possible blockages hydrate and move through their system. I also use this to help dilute bladder sludge. Obviously you are not going to get sub-q’s without a prescription.
I would not do an enema myself but feel quite comfortable administering fluids when needed. I think an enema could cause more problems if you don’t know how or when to administer than sub-q fluids.
Obviously you need to talk to your vet for any of these things and your vet needs to feel confident you know what you are doing.
I would feel more concerned about administering pain meds and gut motility drugs than sub-q fluids if you don’t really know what you are doing.
Also if your rabbit is having problems you should take them to a vet as soon as possible – you would just do sub-q’s to get them through a difficult time until you can see a vet.