I've tried to mimmick several different synths with the P12, it's insanely versatile and can get in the ballpark of alot of synth sounds for practical use. Obviously not for nitpicky AB testing
(I'm also saving up for a P6 atm). And don't forget that the P12 is already mostly analog, it's just the OSC's mainly that's digital, but they do mimmick analog oscs already, take a look in an oscillioscope.
First of all, there's several forum posts out there on how to make the P12 sound as analog as possible, including things like using the osc slop, gainstaging the oscs lower and then makeup with the drive knob, introducing extra subtle slop via a slow random LFO, adding some very slight glue effect with the distortion, etc. Also by nerding out on how a particular synth guides it's users to tend to make certain sounds on it, you can get alot closer to that synths character. After listening to alot of P6 demos and knowing the interface and features I've done some specific sounds that's probably my best patches on the P12, just having something to aim for helps alot.
For the P6 sounds I really like, I find that alot of the key is to first try to do as much as you can with the OSC's, try to introduce natural analog sounding movement between osc 1 and 2 (only using the waveforms present in P6) and by manipulating the PWM with LFO (and don't forget regular osc detune to make them move against eachother). Also use all the other tricks for analog style patches such as slop and more. Once the oscs by themselves shine, that's when I go for the filter, and I find that alot of P6 patches make use of the HP filter, so a touch of that helps alot, and some nice filter env can do alot. Personally I like to have super short to zero release time on my VCA, but by adding more of a tail to the sound, that helps to make it sound a little more sloppy and analog. Similarly you can actually mimmick a limited slice of OB6 flavour by using the 2 pole lowpass with high resonance (obviously it wont get all the way there, but for practical use you can get into the ballpark, obviously missing out on most of it by not having access to the filter mod). A final trick is to introduce a faster but still subtle vibrato to one or both of the oscs, and play around with the waveform, I've found that strangely that can do alot. Also just utilizing the mod wheel the right way and making the vibrato sound good does alot.
By the way, if you make the patch stacked but make part B silent, you'll get 6 voices instead of 12, meaning you'll probably get similar voice stealing and glides that you'll get on the P6.
Finally, you can get the delay to kind of almost sound like a spring reverb (use the low feedback mode), and you can also make it do flangeing and chorusing, so that's something to play with to add some final sweetening, but I usually go for a dry sound or a fairly subtle reverb style delay patch.