About the charge down -> up moves

For the charge down -> up -> attack key moves, such as Gen’s Oga and Vega’s Barcelona Attack, am I supposed to hold down+back or just down? It never seems to work if I just hold down by itself, then press up. I’m assuming it’s more of a diagonal motion (charge :db: -> :uf: ) rather than a straight vertical (charge :d: -> :u: ) motion? Yet in all of the guides as well as the in-game command window, it just says :d::u::k: .

db works

its just that gens oga takes extra long to charge

and vega might have input conflict with his flip kick if you’re not accurate with the command.