You have to start from the current (more exactly, the I²dt ...) your fuse or circuit breaker can accept without blowing or tripping.
You must choose the lowest possible value of resistance.
For a 1000VA 230V transformer, you must use a fuse of 5A of higher.
Than peak current may reach 2 x nominal current for a short time without blowing the fuse.
Peak current must be limited to 10A.
Peak voltage is 325V.
Limiting current power resistance should then be 33R.
As this resistance must only be in circuit for a short time,(1 or 2s), average power dissipation will be low and I think that a 10W power resistor will be enough.
Best way is to try it...