I can have WILD with WBTB easily, like within 1 min.
I know this is because I am already in REM by WBTB.
Recently, I had tried WILD without WBTB but failed. 
It took me about 15 min to have those hypnagogic sensations, e.g. numbness of limbs and weird sounds, but the these sensations just did not develop a complete scene.
Most of the time, I lost my patience and consciousness after 60 min, and sleep naturally. 
Can anyone succeed in WILD without WBTB? How long do you normally take?
When do you do WILD then?! Right away when you going to sleep?! If you can’t do it without WBTB it means that you are doing it in wrong time, as you already mention REM you should know that because for first REM period takes around 90 - 130 minutes… So there is really no much point in doing WILD without getting some sleep first…
Then, I will try to remain conscious for 2 hrs
Why would you do that?! It’s much easier to do it with WBTB. It’s unnecessary trouble. Well if you do have time on your hand you can experiment but if WBTB works for you I see no reason why you should lay in bed for 2 hours waiting for REM to kick in if you can sleep 2 hours, wake up and enter the dream in few minutes as you mentioned… 
Because I saw that every guide suggests wbtb.
And I wanted to challenge.
I will try for a few nights and post results here.
I had used sun eye method in the past few nights. I found it is possible to induce ld without wbtb. But the dreams were very short.
Good luck on your attempts. I have managed do succeed on it only a few times and certainly it took more than 100 minutes to get there, in a very very low success rate.
It’s not just patience, there are other issues that I still do not understand, please report them if you find something special.
That is another reason to use WBTB, the dreams get longer during the night. So even if you can do it on first going to bed, the result isn’t really satisfactory.
Y’know, I actually tried the WILD technique without WBTB last night.
At first it was going pretty well, I felt several hypnagogic sensations but always remembered to focus on my breathing through my excitement and feel them passively. Then my arm started hurting. Thinking it would go away so long as I didn’t focus on it, I continued to focus on my breathing.
After awhile the pain wasn’t going away so I decided to stop because I took the pain as my body’s signal of saying “Quit it!” and listened. I’ll see if I can get more success with trying WILD with WBTB.