Applying for Government grants (US/Canada)? Thoughts on Leyton?

I have received some advice on applying for Government grants and would love to hear about some experiences. For context, I am in Canada and my co-founder is in the US.

Meanwhile, a company called Leyton reached out to me about this too:

• they work on a commission basis to help startups figure out which grants they can qualify for, and assist in applying.
• if we don’t get any grants they don’t charge us anything. When we qualify and receive grants, they charge a percentage of it.

Anyone here has had experience with Leyton?