The best way to cash out as close to $150 as possible is to play many hands of the smallest denomination possible. So 600 hands of nickel video poker was probably the way to go.
If you're trying to maximize your expected return, then you want to play the game with the highest expectation. Possibly VBJ if it pays 3:2. Video baccarat may have been the choice if the VP paytables sucked.
If you want to maximize your earn per hour, then putting it all on one hand is the way to go.
I prefer eCraps, eRoulette (but almost no machines will accept FP on them) or VP.
As I recall, eCraps, you're looking at insurance of about 1.5%, eRoulette, 5.5% and VP is just VP. Irritatingly enough, I get so many natural 4 of a Kinds when playing nickel DW when trying to grind out my FP.
For the Cosmo promo, I did 5-line penny poker (25c per round) on their 100-play machine. Surprisingly, they offer 7/5 Bonus (98.01%) for pennies with no min bet requirement. Took me about an hour to play through, and I did reasonably poorly, I got $89 out of $100 back. Video BJ would definitely have been faster with similar payback and probably lower variance, but I like video poker...lol
If you can find Video BJ at 25c a hand with ~okay rules (1:1 BJ, S17, DOA, split once, no DAS) (2.88% house edge), then you would win $145.68 back on average with a standard deviation of $6.675 per 600 hands. So roughly 95% of the time you would expect to be within 2SDs, so roughly 95% of the time you would fall between $132.33 and $159.02. Of course if time is valuable to you by any means, this method is bad since it would take at least an hour for many people.