Miller calls it an option of last resort exclusively to limp home but he praises the fluid-type sealers to fill pinholes. "Just don't use those pellet-type sealers," he says. "That stuff (goes) right into the water jacket and tanks." He prefers Wynn's but it's tough to find and our local (and trustworthy) parts house heaped praise on Zerex's version.
Should you elect to run flex hose ensure that the metallic component doesn't touch the radiator. That represents a direct path for the engine to seek ground through the radiator regardless of antifreeze or grounding integrity. The same holds true for the wire support in rubber flex hose. This one touched the water neck and the radiator, hence the powdered rust.
Introduce a metal to the cooling system that's less noble than the other critical metals and it will take the brunt of galvanic corrosion. Marine shops sell these zinc pencil anodes in brass NPT plugs for less than $5. Replace the petcock with one of the 1/4-inch jobbies. Technically mixing brass with aluminum is bad but a galvanic reaction can't exist there so long as the zinc stays intact. Note that these won't control electrolysis.
Test your coolant's pH level with litmus strips. A pH lower than about 8.5 indicates an excessively acidic mixture and an environment rich in electrolyte. Consider this worthy of a flush and refill with fresh coolant.
Consider an adequate overflow container mandatory. If exposed to air when hot the protective elements in even the best coolant will form solid deposits. That blocks tubes and compromises the coolant's ability to prevent electrolytes from forming.