My first mould with tooling gelcoat was perfect!

Depends what is causing the pinholes. I've only ever had 2 types of pinholes in tooling gelcoat. One is caused by air entrapment behind the gelcoat when applying the skin coat. These are then unsupported voids behind the gelcoat, which break away and leave pinholes. These generally aren't apparent straight away, more after a few days/weeks. 

If you're using EC's epoxy tooling gelcoat, then I've found this to be much more prone to trapping air and leaving behind mini-craters on the surface. It's a fair bit thicker than the Unimould gelcoat and can be tricky to apply well, especially in corners where it might naturally pool a little more

It's also near impossible to carry out good repairs on, as it doesn't respond well to flatting and polishing so I try to avoid using it now on anything but simple shapes.

On balance, I feel the Unimould system is much better to work with, even having the unavoidable fumes to contend with

Ah yes, apologies, I misread the first post thinking this was using a vinyl ester tooling gelcoat.