I would like to ask some tips how to fix bubbles in a completely cured resin?
Unfortunately some bubbles has showed up at the end of the first stage so i couldn't fix it at that moment because it was partially cured.
After the finish of the second stage and cured completely, i have drilled some test holes into an off-cut piece to check what's going to happen when i filled it with resin again. I cleaned the holes with white spirit and vacuum cleaner so the holes were fully clean. But i am not really satisfied with the results. Is there any way to fix those bubbles?
I attached 2 pictures (bubbles and test holes) I have used Glasscast 50

Unfortunately you will struggle to get those deep bubbles out.  You could try drilling or grinding a hole down to them then re-filling it, but chances are it may still show up once cured.  Bubbles near the surface are easier to deal with.  Also the fresher the resin pour, the less likely you will see the repair as there fresher the pour the more cross-linking will occur.  

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant