"Can everyone learn to use these techniques, and how easy is it?"


Yes, seemingly everyone can use them. Some people are better or faster at it than others, as is true with any skill. Regardless of where you fall on the skill continuum, you will see progress if you use these deep relaxation techniques regularly.
 As to the part about it being easy, the answer is both yes and no. It is relatively easy, in that the techniques are simple, but it might be considered difficult because our minds are a strong beast to tame. There is no free lunch, and you should be highly suspicious of any claims that something truly worthwhile is going to be effortless. It does require some effort because these techniques are a skill and the more you put into it the more you get out.

"What does it feel like?"


deep relaxation is a natural state of mind. Everyone feels different. Some people may feel quite mellow and may feel light or weightless. Some may feel very heavy, as if sinking into a chair. The main thing that people say, is that they feel relaxed and at ease, with a sense of well-being.