There is a way to make expert a lot easier on yourself. Basically when out on track you are able to pause, switch on assists and continue racing. Then before ending, switch the assists back off and it still counts for expert. The step by step guide is what I did and got the trophy with.
Step to follow:
* When you start a new season that you want to make your expert season, select expert difficulty in the pop-up menu when you are about to start a session. Make sure you do this for the first session of the season (Practice In Bahrain). You shouldn't change this throughout the season and it should always say expert when starting a session.
* For Practice and Qualifying turn the assists on once you are out on track. I also switched them off before returning to the garage and restarting. If you are out on track right at the end of the session make sure you pause and turn them off before you cross the line and the session ends.
* For Racing I turned the assists on when I was sitting on the grid waiting for the lights, I turned them back off if I was restarting the race and I paused before crossing the finish line and turned them off at the end of the race.
* This isn't necessary but I would recommend it. Back up your save game regularly. You can back up to USB at any time and reload to your console if things go badly wrong. If you get a string of bad results of forget to turn off the assists before it auto-saves. I'd say do it after every race result you are happy with. Alternatively you could turn auto save off in the MyF1 menu and save manually. I'd be in favour of creating backups though since It's very easy to forget to save before quitting.
This exploit still works on version 1.01 of the game.