so my take on it, is that everyone is different, i reckon in mma getting into rubberguard is super easy, its given to you most of the time when a guy punches. try and grab the overhook and go straight into new york chilldog or kung fu move. (flying NY/chilldog/kungfu move) when working rubberguard from mission control and you wanna zombie but cant, then in mma you can throw some elbows until they defend their head and then its easy to pop the zombie through. half guard is hard to say what is best because especially having so many guys that are good wrestlers these days you wanna be careful when going into dog fight and having to face their whizzer, you could manage to get to dog fight and then have them smash you and then pass you. theres always the electric chair which eddie just showed on the newest MTS which works so well its ridiculous. and thats a perfect sweep from half guard. or get better at jsut recovering full guard. rubber guard works really nicely from here because they give you a overhook (or they give you an underhook and you can work sweeps with perfect double underhooks and lockdown) grab the overhook and then do one of the stomps and hop into flying NY Chilldog or kung fu move.
takedowns arnt really my forté but if its really hard to get underhooks there are some sacrifice throws and things you can do from there, suplex? really im not that sure about it sorry, Then again there is always third option, pull guard.
i hope that helps.