It’s a common story. I have two google voice numbers to manage. Well, 3 really, but the 3rd is for my hobby business, so I’m just leaving it out of this.
The reason I have two is, well, that really doesn’t matter. I have two GV numbers, I’d like them both to ring on the same mobile phone, and manage their filter lists separately. 
However, as anyone who’s looked into this knows, Google won’t allow you to forward two GV numbers to a mobile number. You can forward two GV numbers (but only two, not three!) to a “normal” phone, but not to a mobile phone. I’m sure there’s some reason for this, probably having to do with carriers not liking it, and Google has to be friendly with carriers.
As soon as you don’t treat a phone as a mobile phone, the options to get text messages to it change, and voicemail management changes. 
Bottom line, there’s no way to do this and have the same relatively seemless support for your mobile that you do with a single GV to mobile setup, but if you really want to have two GV numbers ring on your phone, you can approximate the experience.
Another complexity, if you have an Android phone, the first gmail address you pop in there is your primary account. That’s the one that will be used when you use the google voice app on the phone. The other number will be a sad step-child, you’ll be able to do everything, just not as seemlessly.
First, let’s just get the voice bits done. Go to account “A”, set your mobile to “Home’, and do the verification bit, if you have to. Then, log out, log into account “B”, and set the mobile number to “Work”. OK, so now the easy part is done. Both phones will now ring to your mobile phone.
Now, you have two other things to set up, SMS and voicemail. Let’s start with SMS…
Since you’re already logged into account “B”, we’ll set that one up first, and assume that one is the sad step-child account, not the primary number, if you’re on Android.
OK, so this isn’t going to have pictures and annotations, if you actually follow this, good luck, and I hope I describe it well enough. I wanted to be able to remember what I did for when I want to undo it again someday.
First thing we’ll do is set up your forwarding number. First, find your email-to-sms gateway here: http://hacknmod.com/hack/email-to-text-messages-for-att-verizon-t-mobile-sprint-virgin-more/. If your carrier isn’t listed, then Google it. If you can’t find a way to send email to your mobile number and have it converted to SMS, you’re kinda outta luck here, or will have to just deal with SMS messages only coming in as regular email to your gmail account. Of course, you may want to do that anyway, if you don’t want to use/pay for actual text messages, which is one of the benefits of the single GV to single mobile number setup.
Go into Google Voice and under “Text Forwarding”, check the box.
Now in Gmail go to Settings and “Forwarding and POP/IMAP”, and add a forwarding address to the email-to-sms address you found earlier, if you’ll want to get SMS messages when you get a GV SMS. When Google sends you the confirmation, it’ll be a full-sized email message, but fortunately, the confirmation number is at the beginning, so just enter that first number into the validation area, and viola.
Now, send a text message to your GV number for B. Then, go into gmail, pick the message, and set up a filter for messages like this. Remove everything to the left of the “@” sign for the from (@txt.voice.google.com), and forward it to the forwarding email address you just set up.
OK, voila, SMS’s to your GV number will now arrive at your phone as SMS messages.
Now on to voicemail…
If you’re happy with just finding out about voicemail from getting an email to your google account, just go into Google Voice settings, and check the voicemail notification box, and you’re done! I wanted a little more notification, so I added another gmail filter, this one using voice-noreply@google.com as the filter, and then I forwarded the voicemail to the same email-to-sms account earlier. You might guess, I have unlimited messaging with my account, but even with the somewhat common 1k text messages, I don’t get enough calls to fill that up.
OK, you’re done with account “B”.
Now, if you have an Android phone, you’re basically finished. You can already get notifications for any GV activity on your primary number by using Google’s GV app for the phone.
But, if you don’t have an Android phone, or want to get all your messages exactly the same way, simply follow the same instructions, but using your other GV account. I actually send voicemail notifications from both accounts to yet another email address, and I also have notifications from Xfinity going to the same account, so voicemail anywhere all gives me notifications in a single email account.
There you go. A bit kludgy, but it does get the job done.