The model in the first video makes a point of telling the audience to just enjoy the act; not to worry about looking strange! Any experienced pronunciation instructor will tell you that "tongue exposure" for many learners from many cultures is very bad form, to put it mildly. Some advise sticking the tongue way out and then drawing it in as the TH is spoken, scraping off the tongue and teeth. Others recommend just "putting the tongue on the upper teeth," etc. As in working with vowels or rhythm or intonation contours, precise haptic anchoring is the key to most efficient consonant repair as well.
The TH haptic protocol includes one unique element: (a) Sensitize the tip of the tongue--See earlier post on the "Starbucks" technique for that. (b) Place a coffee stirrer stick up against the lips, with the narrow side (.25 cm) touching both lips lightly. (c) When the TH is articulated the tongue should push forward and only lightly touch the stick but go out no further. (d) if the TH is voiced, the forefinger of the other hand also touches the vocal cords, as in the s/z/sh/zh protocol described in an earlier post. This is one case where you can, indeed, "beat that (the problematic TH sound)--with a stick!"