There wouldn't be a harder working, or fitter, jockey than Paul Hamblin.

The Cranbourne-based rider makes himself available at trackwork for anyone and when the track closes will head off to a trainer's property to do some extra work.

It's not unusual for him to ride up to 35 horses a day, except for days when he's at the races trying to boot home a winner.

On Sunday he heads to Ballarat where he has a book of eight rides, six over jumps and two on the flat.

"It'll be a tough day, especially in wet conditions, but that's why you've got to stay fit," Hamblin said.

Among his rides is Nishiazabu in the Grand National Steeplechase, the feature race of the day.

Success on Sunday would give Hamblin a third Grand National Steeplechase for the year.

He won the South Australian version on Nishiazabu at Morphettville in June while Upper Cut took out the New Zealand Grand National at Riccarton last Saturday.

"It was a bit easier over in Adelaide," Hamblin said of Nishiazabu's win.

"There'll be a bit more pressure this time around but you're always a chance if you're in it."

Giving Hamblin some confidence is Nishiazabu's ability to run the 4500m.

Trained at Strathalbyn in South Australia by Kevin and Heather Frew, Nishiazabu finished second in the Great Eastern Steeplechase over 4950m at Oakbank in March.

It came two days after he gave a dashing display in the Von Doussa Steeplechase.

Hamblin will be joined by fellow Australian riders Steven Pateman, Brad McLean and Braidon Small taking on visiting Irish jockey Katie Walsh and her Australian-based Irish team mates John Allen, Shane Jackson and Martin Kelly in a three race international series.

Walsh is trying to emulate her brother Ruby's win on Bashboy in last year's Grand National when she partners I'll'ava'alf on Sunday.

A winner of Ireland's Grand National Steeplechase, Walsh says a Grand National win in Australia would certainly look good on her CV.