The point of those tariffs were to overcome unfair practices such as dumping. Using subsidies after the tariffs seems self defeating.
It goes without saying this all comes at the cost of everyone who's not receiving the subsidies.
You want to boost domestic production but you also don't want to stifle domestic adoption.
So if you implement both tariffs and subsidies, consumers can still pay the market price but will buy up all domestic production first.
This sounds correct to me? But I haven't given really thought about it deeply yet.