You will have to wait till official 5.4.0.Final release in few months. Atm installer from latest hudson release isn't even starting up, deployments fail.
Atm best You can do now is to study 5.3 docs, study API and think of hints for developers what things they can change or make better. Like withlist:) Things like features You would frequently use in engine, jbpm-console, human task service etc. And put them on jira for dev team considerations.
We all hope to get some real fix for that asap.