Thanks.
When I started I found the main difficulty was holding the item without it distorting and getting fingerprints all over it. I then remembered a documentary on facial reconstruction (in the days before non steam powered computers) where the artist/anthropologist used pegs to provide depth information (and an anchor).
I would suggest"making" a practice tool, comprising a piece of 2 X 3cm wood about 10cm long (dimensions not really important just handy to hold), wrap it in cling film and drill two holes to suit either rod or paper clip.
The greenstuff should not stick to the clingfilm so you can remove it, if you like it, you can use it, if not you can try again.
I use Evergreen plastic rod.
I find that it is best to make one stowage item at a time, a bed roll is about 4 - 5mm of greenstuff strip. New greenstuff is a lot more pliable and sticky (the first tanks used some I bought along with the GW fellowship Of The Ring game, that was hard work).