starting mediation ...
If you have not yet agreed with the other parties to try mediation, consider inviting them to attempt settlement, mentioning Halsey and other relevant case law.
This template may assist. Consensus Mediation can approach the other party for you, if you prefer.
Use the Mediation Checklist to guide you.
Remember, don't leave it too late to mediate - whilst you need to gather and evaluate enough evidence to properly understand your case on the merits, delaying settlement discussions may cause unnecessary expense and anxiety.
For the future, consider inserting a mediation clause into your contracts. Whilst there remains some debate about the enforceability of such a clause, the point is not about enforcing it, but rather allowing you to raise the possibility of mediation without 'loss of face' or showing a 'sign of weakness'.