I tried it yesterday. I had a less intense O, but the rest was great, and POIS symptoms were much reduced compared to "normal". I think indeed it is related to the refractory period.
I took 22mg of zinc in the morning (I take this every morning), 200mg of P-5-P (active form of B6) and some magnesium bisglycinate right before sex.
The combination of these supplements is similar to a supplement called "ZMA" which is used by bodybuilders a lot, apparently.
I'm not sure about the long-term effects of taking these supplements though.
After O, I put a little but of thiamine on my tongue (like 30mg or so). For me this tends to reduce the brain-fog a little, but if I use too much (more than 100mg), it makes breathing more difficult.
By the way, I'm also taking B5, taurine, ALA, copper, B12, methylfolate, myo-inositol on a regular basis.