Hi all, new to the site.

Ive played with fiberglass before and for this i want to make a female mould from part of my aluminium motorcycle frame outlined in red on the picture below. The mould would then be used to make a carbon fibre male cover to fit over including covering over all the bolt access holes and create lips round certain edges to act as clips for it to clip on. 

Ive read up on that process but I need to start with a completely smooth surface before applying the release wax and the gel coat etc. 
The surface of the aluminium is very slightly braised/dimpled which is in contrast to the rest of the frame which is totally smooth. If it was smooth then I could use the frame itself to make a mould.

Main Q is is there any kind of air dry clay/body filler I can use to create a completely smooth surface over the aluminium (including filling the access holes)? I would then apply the release wax to it and subsequently the gel coat and fibreglass.
I want to be able to remove the clay/filler after as I don't want to chamge/ruin the aluminium surface permanently.

I also understand that by using clay, I'd also need to apply waterproof damp seal and allow to harden prior to the wax.

Thanks in advance,
Phil