You have the same problem like players who can't play 2-4-6-8 tables at the same time. YOu find it hard? Then you need to know that body and mind are getting used to anything during 3 weeks. If you can't play well at 6 tables at the same time, then practice by playing 9-10 tables for 3 weeks. It will be hard, nearly impossible, but you'll be used to it during 3 weeks and when you'll feel yourself comfortable at 10 tables it's great time to step down to 6 tables, cause that was your goal, so after having hard times playing 10 tables you will be surprised that 6 tables is a bit boring and slow.
Now back to your question - You have to change gears during the tournament, depending on stage. When you're in the money it's time to play more loose and more aggressive, specially against those who prefer to play tight. You have to steal blinds even with trash hands, if your hand is 27os, but you are in late position and remaining players are tight and not really aggressive then you have to BET and steal their blinds! You also have to punish the limpers, if they limp being in the money it means that their hand is weak, they want to play post-flop and see if their suited connectors or weak aces/kings/queens might hit. DON'T ALLOW THEM! Punish the limpers as often as possible when you're in the money. You need to see weak players and use their weaknesses to increase your stack. Such players often prefer to wait, they spend their time bank, they want to limp or see the flop for cheap, such players prefer to stay away from pre-flop allins.
Split the tourney in 3 main stages 1) starting stage 2) in the money 3) final table
during the starting stage you're playing tight, your main goal is to grow your stack and enter stage 2... during the second stage you're main goal is to grow your stack for the final table, this is the time when you have to bluff often, you need to appear strong when you're weak, and appear weak when you're strong, and use it against the right opponents. It's good to change switch gears again and play tighter game when your stack is big enough and you're close to the final, cause payjumps are sweeter during this stage, but when you're entering stage2 payjumps are small, so you can play risky loose/aggressive style. Stage 3 is the most important, cause most of the prize pool money are there and payjumps are really nice, so it's great to switch gears again to very tight and very aggressive. You can keep sitting at the table with 10-7-5-3BB stack, cause anything can happen now, you can see several people busting before you and you can also have progression working for you, in just 2 double ups your 5bb stack will be 25BB stack... Keep it in mind and wait for premium monster hand until it's possible, and let other players do mistakes.