I'm interested in hearing experiences on what companies or custodians work best, what pitfalls to watch out for, and any red flags during the process.

Depending on area, coverage needs I have seen varying carriers best fit the policy needed.

(that policy was cancelled by the carrier and I will be getting a separate policy)2 hail damage to Tennessee property  and water damage due to storm (claim is in process) Another Tennessee property now has had a water pipe burst in the kitchen ceiling and flooded the whole house. 

At least most cell carriers will auto-block them. 

There were some red flags prior and I should have trusted my gut on those, $2500 lost. 

In the 2024 insurance market, CA is hard to place, so even though you could force them onto a single policy, it may be more economical to keep them separate.I'll send you a note with the carriers who can do this for you.

Your insurance carrier will decide who is liable, and if it is the other insurance carrier then they will file a Coordination of Benefits with the other carrier.

I obtained the umbrella policy through their "agency" which finds other carriers for their members.

Many carriers are including exclusions for GC commercial general liability coverage and professional liability coverage for engagements involving condos and even stricter exclusions when dealing with conversions.

As far as red flags, if you don't seem serious/ready that will turn some agents away.