There are two main ways to smoke hash oil, one is with an oil rig, the other on a spliff or joint. Smoking hash oil with an oil rig is the same as smoking other wax dabs with a rig. The basic process is described on our page here: https://www.ncsm.nl/english/best-ways-smoke-wax-dabs You will need an oil rig, titanium nail, butane torch, and a carb cap. Super heat the nail, apply the hash oil with the dabber end of your carb cap, cover nail intake with the other end and suck in the smoke.
Here’s what I would do to try to salvage it. Filter the sludge out as much as possible, use a cheesecloth-lined strainer or even better a fine mesh bag like used for making nut milks. Then put the remaining butter and water in a container and put it in the fridge or even freezer. The butter should separate and harden on top. Hopefully, you will still have something you can use. It’s probably not going to taste very good, but you should be able to salvage something.
Many people know to decarboxylate cannabis in the oven first, but it’s worth noting here for anyone who doesn’t know or doesn’t see the point in doing so. You can skip this step and add your raw cannabis to the slow cooker to decarb in the oil, but you might find that this longer oil soak simply worsens the taste of your cannabis oil. It’s also more difficult to control the temperature in a slow cooker and you risk burning off essential cannabinoids, but in an oven, you can set the temperature low and keep it steady.