Can you use cooking oil instead of shortening?
Spectrum Organic Oils has a palm oil shortening that is solid, in a little tub. It is a viable replacement for tallow or solid hydrogenated cooking shortening for baking and cooking purposes. If you want to make soap or candles, and would use it to replace tallow, I don't know if it would work. You can experiment, or email the company and ask them.
Yes, but the results might not be the same. Liquid oil and solid shortening have slightly different properties. You might need to use slightly less oil for similar results, when "creaming" shortening the results do not work for oil, but this step would be dispensed with when using oil. Butter or lard, which shortening was designed to replace, will get the same results as shortening.