Hand-sewn button holes for trousers?

[Schneiderfrei]

Iso 10 is best for domestics. 

Singer oil is faultless, Lily white is popular in the US.

Hydrolic oil is iso32, although it may have colour.

Bear in mind that the machines are engineered to have a specific gap between the moving parts. 

This means that the iso of the oil is important.

[PGithens]

i can't help with the machine issues and it sounds like you've gotten some great advice on possible help, but i've made buttonholes by hand on my husband's 18th century garments and they have been very sturdy - even without gimp for support. the only one that gave it up was one on his breeches that I had not sufficiently supported with some kind of interfacing behind it.

in my opinion, the hardest part of handworking buttonholes is making sure the interior fabric is caught when taking the stitches. having even stitches comes with practice.

just take it slow.

after your first 10,000, you'll almost be a pro. 

[Schneiderfrei]

Spot on PGithens.