Years ago, when I was playing a lot of banjo in an old-timey string band, I experimented with fake fingernails. I used a slightly different method of layering superglue with facial tissue. Ultimately I rejected that because of the high maintenance required. Being blessed with nails more like horses' hooves, I just use my natural fingernails when I play that thumb picking style like Merle Travis/Chet Atkins.
JimK