Use rare candies you could get them at the pokethlon dome using points
Get on the magnet train and it will take you to Goldenrod city. You can back and forth between johto and kanto easily using the magnet train, but it's not essential.
Train you Pokemon I guess.Cyrus is very Tough
Train it.
You win at Pokemon battles if your Pokemon are tough, if they are not they will fail. Train more if you're having troubles.
go to magnet train manger and ask him to give you a train pass
At the Elite Four or battle NPCs with Pokemon the same level as your one.
Goldenrod City
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Keep beating the elite four over and over again.
Yeah; I battle him a lot to train my Pokemon because he's got a pretty tough team. No we can battle him only once I tried it
in heart gold cerulean cave in platinum i don't know
an easy way is to trade a bunch of your good Pokemon onto Pokemon heart gold but if you don't have a lot of good Pokemon on heart gold and you don't have another game then train a lot before you get there :)