I rode Trials back in the 70's , but it is completely different than the skillset needed for todays Trials , or hard enduro riding ,, about all you needed with the old stuff was balance and throttle and brake control , now you need to practice balance , timing , sizing up what you are trying to maneuver thru or over , , sizing up how much input is needed to clear said obstacle , and picking good lines on the fly in little to no head time ... what also is a plus that they don't mention much is height , 6 ft. is a huge advantage over someone who is 5'6" or like me 5'9" , I can barely touch 1 tip-toe on my 450R on level ground , should you need to dab , you need to be able to actually touch the ground or you are going to be on the ground in most extreme enduro situations , I watch them regularly , and I think I could do ok doing it , not pro level ok , but amature level no problem , if I could afford the trip I would love to try Erzberg
And I have done some Endurocross stuff on my 450X
If you are looking for a good "in-between" bike , a KTM Freeride is a good choice , it has the basics of a trials bike with larger tank capacity and a more regular bike feel , but also the lightness of a trials bike (though not as light , but lighter than a regular enduro bike)
The biggest thing with hard enduro is , you need to look ahead , and not hesitate on choosing a line , and the line you choose needs to be a smart line , that will not only get you thru that section , but set you up for the next one , and so on , its all about flowing and maintaining momentum ... it does not have to be fast momentum , just consistent maintaining of movement , the more you stop , the more you have a chance at falling over or not being able to make it thru a section or loosing balance
I am assuming you have some farms around you .... see if one of them will give you a pile of old tractor tires , various sizes (loader tires work great as shown in my picture , we stacked them straight up so you were forced to go over the tire , and the ones on the ground were filled with the bark I am riding over , we also incorporated a shipping container to go thru (doors open on both ends) , and you can fill the tires with dirt or bark to make them more manageable to go over , same goes for using the bark as a obstacle , soft bark is actually hard to go thru , especially when forced to go slow because you just went over a loader tire , lay the loader tires out about 3-4 ft. apart , so you have to either jump from tire to tire , or step down/up to each , a fallen tree makes a good jump log or series of them , even one to ride along the top of inline with the layout , you can either spike them in place so they don't roll or build up dirt/rocks to hold them in place .... set yourself up a small (depending on the area you have to work with) course , that you can circle around and take the obstacles from different directions so you have various options to choose from , when going thru them .....
You can see more of the course layout I did in this pic , basically the tires , container , bark pile , railroad ties and logs made for a challenging course , I added this section for some off road races we did at the track when my friend was running the place (the track I currently ride) as a challenge section ... , then it was fun just to ride it on its own as well for a little fun , it actually can go into a loop back over top of the container then back thru it , we also did mud drags (you can see the course in the background), and 4 Stroke National , and WORCS races there , along with MX
Hopefully that gave you some ideas and tips .... I don't know everything about it , and far from a pro at it , but I have done a bit of it ...