What's the fastest compliant way to get more Google reviews?
Ask the customers you already serve, all of them, within hours of each job, with a direct link. Google's own advice is plain: "you can ask customers to visit a Google link or scan a QR code." Start by making sure every job gets a request; refine the wording later.
What Google allows, in its content policy: merchants may "Solicit or encourage the posting of content that does represent a genuine experience," "without offering incentives to do so or attempting to influence the rating or the contents of the review." So ask for an honest review, don't pay for it, don't steer the stars and don't tell people what to write.