The way I usually raise employee obedience on the cheap is through the combination of the daily compliment/insult and performance reviews. If you don't rush to get the employees to 20 sluttiness, you can use the review option of punish for bad performance > threaten to fire > cut pay (when they volunteer that option) to get a big boost in obedience and paradoxically, happiness. If their happiness is over 110 (120 is safer) you can insult them daily to get another boost in obedience. So I alternate complimenting and insulting them daily while keeping sluttiness lower than 20 (so they don't offer to let me "use" them instead of cut pay) in order to exploit the periodic reviews until they're over 160 obedience.
Other options for family obedience are Mom's bedtime outfit crisis, Sis's morning/evening instagram, morning showers, and stripping. Obviously Sis's instagram is the cheapest and most reliable of these (and the options fulgartech mentioned above are also being more reliable than crises) but if you choose your own outfit for Mom and Sis in their outfit planning you can get a pretty good boost in obedience. It's slow going (the cousin really is a chore) but blackmailing her is good for obedience. Once you have a good +sluttiness/obedience serum, blackmailing her to take a serum and then molesting her afterwards can also raise obedience if used like I describe below.
The way I exploit temporary serum obedience boosts (not just for the cousin tho) is to use them to enable ordering a girl to do sex stuff she wouldn't normally agree to. If you get a -happiness hit on a chosen sex position, that means you "ordered" her to do it and she's only agreeing out of obedience. IF you cum in that position, she'll get a +3 or +5 boost in obedience. You can also use a one-time "quit while she's close to cumming the first time" to get her to beg for climax and get a +2 obedience boost, but only if she's not low obedience. If she's low obedience she'll take over instead and lose obedience. That's one of the things that makes the cousin the worst, because she's already low obedience so you really can't exploit making her beg for it until you can get her over 100 obedience.