only time!
you can not expect your trust rating to go high if you are in the forum for a short time. you should start your services, use trusted escrows at first. build up trust over time. it might even take more than a year to build that kind of trust.
Absolutely, if building your trust rating was so easy then there were so may trusted people out there but there aren't, it takes too much time to build your trust lever and for that you need to be as good as other trusted members on the forum, do legit trades with others, give loans, sell goods etc.
You will reach your goal with the time if you do so.