Yes to the notch cut with a hacksaw. One notch and try the easy out or several and pick out. Try one then the other.
Either heat cycles (to loosen corrosion grip but brass really shouldn't have much in a coolant hose) or cold to shrink and losen...either will work...in this application I like the cold but if heat is handy, start with that.
The internal pipe wrench is nice too if easy to get and not too much $$$$.
Home Depot. Pretty inexpensive. I bought a single but the link is for a set. I used one to extract a broken off shower arm in my home. Worked like a champ.