The easiest bowing strings I’ve ever played were D’Addario Kaplans. The set of lights on my Arvi were like butter. They sound fine, too, but don’t add much color or projection.
I flirted with Spiro Weichs on the Arvi, too. They were very bright and projected very well, and weren’t bad under the bow, but I don’t think they blended well in the section.
Currently my Kimmel has Flexocor Deluxe on the top 3 with a Permanent E. I really like the Flexocor G and D. The A is pretty good, too, but not quite as nice. I had a Flex Deluxe E originally but it sounded bad and wolfed. The Permanent E on ameliorated the wolf and the whole bass responded better, but I’m still not quite satisfied with the E sound - some days it bows well and sounds good, but others it’s a little wimpy. Since I got the Kimmel, the Arvi is sitting in a bag in the corner, I think it’s got a full set of Flexocor Deluxes now.
I like the Flexocor Deluxes for their brightness and clarity, without being too bright to blend. They bow nicely too. My teacher uses Permanent G & D and Corelli 370M A and E, and I wouldn’t mind trying that. I’m also curious to try Original Flatchromes, but trying strings is expensive and annoying.
Long ago, I tried Jargars, original Flexocor, and Flex 92. I never thought much of the Flex 92s but I did like the original Flexocor - I recall they were harder to bow but were very responsive, especially to dynamic changes. My arco technique has advanced significantly since then, so I’d be curious to revisit those strings someday.