Getting an editor for a query letter/proposal?

Morning all!

I've been reading the forum for a little while now... it's amazing to read everyone's experiences.

I'm in the process of looking for an agent for my non-fiction book.
I've written the proposal and query, and sent out the query letter to 20 agents. I haven't had any requests from the query letter to view the proposal. Eight have not yet responded either way.

I only sent out the query letters a couple of weeks ago, so I will give it another couple of weeks for the other agents to respond.

So, I'm starting to look at - what next?

I am considering finding an editor to look over my query letter and proposal before I send out to more agents. I did have some writing friends look over the proposal and query letter, but I want to make sure the query letter is perfect so the proposal actually gets looked at once I send it out to more agents.

How did you get your query letter up to scratch?
Did you use an editor? How did you find one?

I so appreciate any advice you can offer ~

Have a gorgeous day

bright blessings,
Leonie