So, I was riding along with traffic this morning and I couldn't avoid riding over some spilled white paint on the road.
Of course, this had to happen because I have a new bike.
My Masi now has some nice new white accents all over the underside of the frame.

Is paint thinner OK to use to remove the new paint? Will that mess up the bike's panit job?
Any tips are appreciated

What kind of paint? House paint? the stuff for the road? What kind of paint makes a difference in what you can do to it.

I honestly couldn't tell, but I'm pretty sure it wasn't paint for the road because it clearly just fell out of someone's truck or something. I'm guessing house paint.

If it's just normal latex paint you can use just water BEFORE it dries up and it should come off. Else you can try pick at it cause I doubt it would stick to the clear coat.

IF you used a wet rag and all it did was smear then you have an oil based paint and need turpentine or varsol. BUT you have to be really careful with this stuff and probably water it down cause it's strong enough to strip your clearcoat and frame paint also! This is a risky procedure cause you might end up stripping your bike paint also.

If it's oil and dried already and you don't want to risk messing up the frame...
Another alternative you might as well grab a brush and "flick" white paint to the rest of your frame and call it a limited edition paint job .

Old school Kona!

Seems to be latex. A lot of it came off with a wet rag, at some spots where it really caked on (right above the wheels), it might take some work.
Thanks! (I obviously know nothing about paints)

You obviously don't want any harsh solvents, but GooGone is safe and may help a bit. Any hardware store should have that. It requires a little soaking, 2-5 minutes, So wat I do to avoid it all flow/drip away: I wrap the tube with paper towel then soak the towel with GooGone, works great for removing stickers.

Adam

I'd try some WD-40 ... it loosens up a lot of things, and it won't hurt your frame.

Soap and hot water will take latex paint off an enamel paint or good powder coat, even after it's dried. It's easier if it's not well set, but some elbow grease helps. Alcohol will also attack it prettywell.

Use cold water when you're trying to remove latex paint. Probably won't make a difference when dealing with a non-porous surface (such as a bike frame), but heat is simply an activator with latex and will aid in setting it.

It's the thick, slick, Dried paint you need to really be mindful of,
and steel Manhole covers, when the street is wet.

Latex paint has no latex in it. It's a water based emulsion of various stuff, mostly very small particles acrylic. It's supposed to be water proof once it's dry, but they rarely are, because of the failure to remove the other non-water solvent from the paint. Heat and soap help get water back into the paint, which makes it soft, which makes it easier to remove.

Ammonia will remove latex paint. This is why you don't wash your walls with Windex. (And why, when you wash your windows with it, the paint around the glass gets all soft and gooey.)

Windex work wonders.

Keep riding it especially on rainy days. If the paint doesn't flake off, at least it will be covered with mud.