[LargeFormat] Lens cleaning advice required

[Gavin Hubbard]

Hi Lads

I picked up a fairly cheap (around $360 USD including caps) Rodenstock
Grandagon 90mm f6.8 from a local seller recently. Apart from some
delamination around one of the internal elements it seems to be in a fairly
reasonable condition. I've shot some film through it and it seems to be in
order.

Homever there are some faint oil/grease marks on the glass that I'd like to
remove. I'm guessing they're probably fingerprint residues(?)

Is there an easy way to remove this residue? I tried using an off-the-shelf
window cleaner but it left some streaking on the glass (removed with
water). Any advice on "LF lens cleaning best practice" would be greatly
appreciated.

Best regards,

Gavin