octoberfest 2633 starter questions

I have been brewing ales for a little while and decided to get my feet wet with a lager. i bought wyeast 2633 oktoberfest and am planning on brewing an oktoberfest/marzen.. OG around 1.054 and 5 gallon batch. i pitched the yeast to a 2L starter two days ago with minimal activity that i can see, ive been trying to take a decent hydrometer reading but the wort foams in my tube quite a bit and i cannot get a good enough reading (is this common?).. i want to brew on sunday (4 days from now) but i want to be sure i have enough yeast built up for this lager (390m cells thereabouts). i have not cold crashed this first starter but i want to step it up another 2 liters before sunday.. can i just add 2 more liters of wort to existing starter and then hopefully cold crash on friday and the starter be ready to decant and use on sunday? i know general rule with lagers is to not rush them and let them work at their own pace.. starter is at room temp now.. my last question is this lager seems really slow, even at room temp, i guess a lager yeast usually dont show too much activity, is this common for this type of yeast? there is no krausen to speak of unless i count the way the starter foams up when shaken, almost like the head on a beer, then quickly dissapates. thanks for all your responses in advance.

I have my first lager in the keezer and it is also an Octoberfest and I used the same yeast you are using. I used the starter tool on this site and ended up doing a 2.5 liter starter. When I made my first starter I would pick up the flask fairly frequently and give it a good whirl. The first time I did this it actually fizzed up and overflowed so I was a lot more careful after that and have since moved on to using a stir plate and highly recommend that method.  I can usually tell the starter is doing something because the slurry level starts to go up and the overall color changes to become a little lighter over time. I think you are probably ok and I would go ahead and do a second starter, not so sure another 2L is necessary but there are plenty of calculators out there including the one on this software.

Since you are on your first lager I hope you have more patience than I did. I would taste it every week or so after kegged and it was ok, but it really got better with time. Next time I make one I won't test it for at least 2 months after fermentation is complete and it is in the keg and I'll plan my brew schedule so it is in the keg 3 months before I want it.

The worse that can happen is you'll have a very good beer instead of a great one.