To get the best chance of smashing 6 sixes, create a custom player and reduce all his bowling skills to a minimum and increase his batting skills to the maximum. Then create two custom teams each totally populated by this custom player and play a custom match between these two custom teams.
This isn’t obvious to do, so here is the detail:
Go to Custom player, edit skills, use Y to access skills and reduce all bowling skills to a minimum. Change Hand to Right and Action to Medium. Y to exit, move to Batting skills, maximise the Timing skill and increase all other skills. Y to exit and move to Fielding and deposit all remaining available points. Only after all available points are used can you press B to go back.
Immediately save custom player, B to go back and click Yes when it asks to save custom player information. (Make sure the custom player picture shows high batting skill and low bowling skill or it hasn’t saved properly)
Go to Custom Squad and create two teams (Team 1 and Team 2 say) with players 1 to 16 selected as this custom player.
Start a custom match (has to be selected to be Balanced for custom teams to be available) and then select Team 1 vs Team 2 and bat first (if you lose the toss go back and restart the match as the other team).
The settings I used for the match were Custom Test, Slog, Exhibition, Balanced, and when you choose the ground I selected pitch type as Artificial.
One more tip – watch the ball as it releases from the bowler’s hand and eventually you get a feeling for the pace of each delivery to time your shot. Took me 17 overs.