The easiest way is to grab the cached video. All you need is just provide enough disk space for it in browser options, set required quality in media player and wait until buffering is done. Some sites have direct .mp4/.flv link in source code.
>>35567 Google it for certain browser. Sure you can find some plugins, but all downloaded files are kept in cache folder, so you just need to find it and pick required file by date or size (as for opera, they don't have extensions, rename it afterwards).
What helps me out a lot of the time in finding Touhou sex-related MMDs is to search for other series instead. Some of the MMD artists who do stuff like Vocaloid MMDs or im@s MMDs may have had Touhou stuff back-logged in their uploads without proper tags to find them.
>>37465 The MMD models scene is a fucking mess, but the easist way to start hunting for models is probably to go to: http://dic.nicovideo.jp/a/mmd%E6%9D%B1%E6%96%B9%E3%83%A2%E3%83%87%E3%83%AB It has a compilation that links to most of the available models. But you'll have to figure out how to download them. Plenty are locked behind passwords, some are told outright, some you have to figure out, and it's all a pain in the ass. One of the primary reasons why I stopped paying attention to that shit.