what do you mean to the escrow, if to the account. I really don't know how but I know some how to increase. It will only increase if there is someone want to add trust to you buy donating first. For example, in the signature campaign then you manage it then if the signature campaign is ended the owner would feedback your performances for being a manager to their project. If he like you for being a good manager, you will earn trust by visiting your profile.
To be an escrow you need reputation and trust, trust and reputation cant be build in a short time, one of the way to get reputation is by getting a good review from trusted member whether you get it from managing campaign or doing transaction, and proactive to help other members can become a good way to start gaining reputation
Yes reputation is one of the things that person will build in his starting escrow service because if someone is lacking of that reputation then less people will trust him, so it is better to build it piece by piece and start it buy doing micro transactions and it will be the start of getting positive trust and having a good reputation and after that it will be a good reputation and an easy escrow service.