First route is through personal contacts/network/referral/nepotism/cronyism. In this case, your strategy of customizing resume and application is an effective strategy as you know your application will be reviewed a relavant human.
The second route is through applying to job listings when you don't have any contact. With this route the chances of your application being reviewed by relevant human is extremely low. In this case, you are better of reaching out to as many opportunities as possible. Pre-application suitability filtering and application customization is waste of job applicant's time. Instead have an standard application and just apply to all positions in your area of interest. Any filtering by job hunter happens once an interested company has made contact.