I already bought 2 of these Orbit DC latching valves and I do like that they require no power to stay on.
The valve control is working fine now, I used a 2 channel relay board I had laying around as high side switches at the input and output of the boost converter, I can open the close the valve just fine with 20V and 2000uF, the valve sees about 18V.
Been shopping for MOSFETs, all logic level 3.3V TO-220 are expensive at $3-4 a pop, may end up using an N-channel AO3404/IRLML0030TRPbF or P-channel AO3407, pretty cheap on eBay ($3-4/100pcs) and relatively inexpensive even at Digikey at $5-6/10.
Since I have no experience with them, perhaps I’ll get the cheaper SOT23 to play with and if I fry them, no harm done 🙂