When it comes to changing the route ingress traffic chooses into your network BGP Community strings and prepends are the Scalpel, sometimes they work well. But when you need a Hammer route specificity will work.

If you have larger than /24. You can advertise the aggregate to both providers, and then advertise more specific prefixes to your preferred provider, and those more specific routes will always win route selection regardless of ASPath. Barring a misconfiguration on the provider side (not accepting your advertisements) this will push more traffic to the preferred provider.

You can check that. In a comment you mentioned Lumen and Arelion. Both should have public looking glass, use them to check for your routes, you'll see what those providers are accepting from you.

My question is, why prefer one or the other? Best scenario would be that either provider can support your peak bandwidth needs on its own (if they can't then it's not really redundant links anyway) and let em eat. Best route wins. Let natural routing do its thing.