the generic "Mucinex" knock off, worked great! But, make sure it's not with any added anything, like a "DM" or something, which is added Dextromethorphan, a cough suppressant. Just the original stuff!
I stated taking it about day 9 or so, when we really started BDing. I took it every morning. Like I said, it worked wonderfully but I did not happen to use it my successful cycle.
I also used sperm friendly "Pre-Seed" my PG cycle, which we loved (actually, never told DH about it but he liked it!) since there was a lot of BDing that cycle and... well, lets face it, a little extra help in that area really, ummm, helps!
I would use about half the recommended dose, full amount being too much... and messy! Plus, not the cheapest stuff so that make it last longer! I got mine at CVS. (But make SURE it's the real stuff and sperm friendly!)
I say try both!