First off I use the pink anti-freeze because it's safer than the green around my dog, plus the neighbors all have dogs and cats.
I also called several manufactures of the pink stuff and asked if it was o.k. for what I was using it for, ( I also use it in the jet-ski's) and they said it was fine.
I haven't had a problem gravity feeding..
I pump all the water out and let it fully drain, then release the pressure. Then I use the muffs (gravity fed) w/ a piece of garden hose and a large funnel pouring in approx 3 gallons until it comes out the tail pipes, pop off the fuel filter, dump out 3/4 of the gas and pour in 2-stroke oil, then re-start the motor while pouring an additional one gallon of anti-freeze with the motor fogging, then use the air pump to pump all the anti-freeze out.
P.S. after seeing this post i'm wondering if it would be better to leave it in,, less corrosion with it full than empty, But, I left a bottle of pink stuff on my porch one cold night and it got a little slushy,,,, so now i'm not sure..