Plastic travel humidor for cigar storage moisture question?!

All I have right now is a small, ten stick, airtight plastic humidor due to cost reasons of a true, Spanish wood humidor and frequency of smoking. It contains a sponge at the top with which I fill with either distilled water or a 50/50 propylene glycol and distilled water solution (depending on how long its been for the PG). I open it up every 3-4 days to let moisture vent as it is airtight. My question- Is there anything that I can put in the humidor that would help absorb any excess moisture, like the wood does on a traditional humidor? a sponge, some type of gel pack? or is it even necessary with the current setup? is my 'venting' deleterious to the cigars or should I keep doing it? Any advice is appreciated as I am still learning! And yes, I know a plastic travel humidor is not for long term storage but its what works for me right now. Thanks!