Geographical location is a large determinate to what you are dealing with. If the situation is bad. Heat really is you friend as the hoses are being scrapped anyways.

I dislike the expression of walk in the park but it does apply with heat in our extreme canadian east coat rustbelt corrosive area.

Part of the underlying reason is it will also break free the nut that bonds with the corrosion hard brake line as well. Beats turning the nut and and twisting the line as well in the process.

We have a system of dealing with really stuck bleeder screws as well. You heat and quench the area around them three times. Usuallly they come right out easily then. It is hopeless to apply heavy pressure to those screws because they will break off flush on many versions of them. Penatrating oil helps with a certain amount of corrosion but you have to let it sit and work. Plus it best be a good type. My problem with recommending heat is not everyone has ox/acet. Although there are hotter burning gasses available for simple torch heads. Even propane will help but it probably may not be enough heat.