I don't think you'll get many marks for copying and pasting large parts of the audit trail, as the style required in the summary document is different. The IFoA's Guide to CP2 says this approach is not advised:
"In Paper 2, you must write the Summary document without the use of template headings and without copying large sections from the Examination Question (including the audit trail found within this paper). Candidates who copy large sections of the information in the exam question and/or the audit trail provided into their Summary document, without consideration of the purpose of the Summary document or the target audience, are likely to gain very little credit from the examiners."
(BTW - I definitely recommend reading this guide if you haven't already as it's got a lot of helpful info in it.)
I'd say you can use the audit trail as 'inspiration' in the relevant sections of the summary, but the descriptions can generally be a bit higher level.
The exception to this is copying across the assumptions from the audit trail - it's usually OK to just bring these across (assuming you haven't changed any of the assumptions you're making as a result of the additional modelling). There's usually one mark available for 'restating assumptions from the audit' on marking schemes.