is there a quick way

In my opinion, to solo/improvise over blues/rock music, theory isn't needed TOO much. Jazz is another thing - you need to know your stuff.

Blues, the stuff you need to know is very simple. What key are you in, and what scale can you play?

The key part is easy - usually whoever you are playing with will say "blues in ___ (G, A, whatever)" or, the first chord is usually the key.

So what posistion on the fretboard? I feel like I've made this post a hundred times. You really need to learn at LEAST all the notes on the low E string. It's not hard at all.

1 - F
2- F#
3- G
4- G#
5- A
6- Bb
7- B
8- C
9 - C#
10- D
11- Eb
12- E

Now take this simple shape (numbers = fingers here)

---------------------1-4---
----------------1-4-------
------------1-3---------
--------1-3------------
----1-3--------------
1-4----------------

(1 = index finger, 3 = ring finger, 4 = pinky)

Right, so now, assuming each finger would cover a fret, take that pattern and put it at, say, the 3rd fret
--------------------3-6
----------------3-6----
------------3-5---------
--------3-5----------
----3-5-------------
3-6----------------

K, so see how that starts at the 3rd fret of Low E? Look up a little bit, and you'll see 3rd fret of low E = G. So you're playing the Gm pentatonic, which is great for blues/rock songs in the key of G.

Now, this is a really simple scale, simple pattern, and simplified process, but it'll get you on the right track.

Taso
That pentatonic form ^ is the one I have tried using the most. Or the one I know the best anyhow.
I been using it like you said according to the first chord of the song and finding that on the low/high E string. Then try to make something up using that form. Just throwing some bends, and hammer on/off in with it.

It's a good place to start. Also, something that helped me was learning Cream's Crossroads - those solos have a lot of licks that you'll be able to use.