simultaneous application of soil amendments
I don't see why you couldn't use both simultaneously. The sulfur is slow acting, and will take a while to adjust the pH in the media. The blood meal is a fast-release source of nitrogen, and should be available to the plants fairly quickly.
Be careful not to overapply either product. Too much sulfur can cause a chemical burn on the roots. Too much nitrogen can affect flowering, and cause rampant vegetative growth.
If you have other questions, I may need more specific information about your particular growing system.