"Self-levelling" compounds are available for concrete but I dunno about wood. As for any of the commonly used stuff, what matters most is what it is applied with. If ya don't have the right tools for the job, it doesn't matter what ya use on accounta it will come out crappy unless yer REALLY lucky. Spare NO expense on the proper tools.

Oh... yeah... many thin coats are better than a thick coat with most stuff.

Keep us informed about what you use, how you use it and what the results are eh?