Once I've made the decision to replace the valves, guides, etc. (which is an easy decision to make), then some level of 'violence' usually comes into play.
This is especially true with older flatheads with mushroom stems and split guides - nothing for me to ponder saving.
With later one-piece guides and 11/32 stem valves, sometimes you can save them, but if they are frozen, rusted, obstinate, etc - get them out any way you can. I've used cut-off wheels and air tools to cut springs/stems. I've raised valves and knocked their heads off with hammers, heck - I even used a big ole' set of bolt cutters to cut the valves stems - whatever gets the job done. Once you know you're not hung up on saving the old stuff - you can get a lot more brave.
Having a large/long forged valve bar is REALLY important - as I can use it to lift the springs up, let the keepers fall out, etc.. I have never used one of the big C-Clamp style of tools - just a real pain getting them into the valley in all the weird angles. I'm sure that if I liked that approach, I'd just modify one to work a bit better - but don't see much of a need.
Anyway, best of luck - take all the ideas you've been given . . . see which ones work for you and get after it. In a few hours of time you'll have it all taken apart.
B&S