You can do it with a midi controller.
Yeah, also....
I dont know about Reaper specifically, or other daws for that matter, but I use LOGIC, and there's a really helpful group of settings within the automation controls.
READ
TOUCH
LATCH
WRITE
These settings allow how the automation is controlled / reacts.
The one most applicable to your question is the TOUCH option. What it allows you to do is adjust whatever parameter your changing WHILE the song plays. (for example if your sweeping the high freq's of a vocal track but only in a certain part, and then want the eq to go back to normal.)
you let the song play... then using your mouse (similarly to a midi controller, or an actual analog mixer knob, fader etc) you control the parameter (cutting the frequencies in this case) and then as soon as your done, just let go of the mouse click and the setting will go back to where you started.
This is AWESOME, and completely cuts out the whole "Drawing lines and dots and a bunch of gay time consuming shit" that comes with automation.
Similarly, the LATCH feature does the same thing, but instead of going back to the initial starting point of the parameter adjusted, is stays where it is.
the WRITE feature lets you completely do it from scratch...
and finally, after all your adjustments are completed, be sure to switch it back to the READ setting, as it will simply interpret and implement your new automations.
haha sorry for the huge schpeal... especially if you arent using logic and now you have no use for this... but check within your DAW to see if you have a similar feature. it will save you loads of time, and its tons of fun!
I was able to control and automate a plug-in based wah pedal using a slider for one guitarists solo take. hahah it was fun!