I have a half dozen systems here and on my list to audition, but I really like the West Systems stuff I have used so far.
West Systems 105 Resin and 206 Hardener is doable if you are good, have all the tools, and are fast. 207 will give you more time, little less strength.
209 is the thinnest mix, should wet out best, lots of work time, LONG cure time... maybe too long for you? If it was just to protect the cardboard, I'd do 105/209 and light weight cloth, and eat the cure time.
207 should be available to sand following day, water clear, up to 3 coats in one day without additional cure/prep. 207 is also good enough as a structural adhesive too. Add 406 colloidal silica in varying amounts to get consistency for fillets, etc.
Alternatively, Get a 105C Resin, and 205A, 206A, 207A, and 209A hardeners and have a "quart" of each to try.