I did a few coats of future on a model and after I was done, I noticed an small area (1/8" x 1/4") that needs retouching with paint.

The paint is an enamel thinned with Mr Color Leveling Thinner. Can I retouch with a very light mist of color over the future?

I'd say yes, as long as the Future has fully cured, say at least 48 hours. I'd also recommend thinning the enamel paint with the proprietary thinner, and lose the Mr. Color thinner, since it's quite hot, and more like a lacquer. This could attack the Future coat beneath.
VR, Russ

If you're not planning any more layers of paint or weathering then it should probably be okay. If you want to make real sure try duplicating the same layers on a piece of scrap and see what happens.

Thanks for your suggestions. BTW the current "Future" coat I just bought some polystyrene sheets and will prep some samples, paint them and coat with future. Once cured I'll try to paint over it with my enamels.

Russ besides the manufacturers thinner, what is a good thinner for Humbrol enamels?

Each country has its names and difference in how hot is the thinner, however I have diluted Humbrol with a little bit of everything, Turps, low odors turps, whitespirit, laquers thinners, mineral turpentine and never have any problems ... i used Humbrol for 30 years

I agree with Vicious about the thinner for Humbrol, I've used Humbrol since I was a kid in the 60's when it first became available to modelers in the States, but lately I've become dissillissioned a bit by it, as I think they've changed the formulation (I just can't get the stuff to dry properly). It used to be the best paint for brushing. But in your case, I'd stay away from any lacquer type thinner and go with a white spirit, mineral spirit, or turpentine. The lacquer based thinners (such as Mr. Color or Tamiya yellow cap) may attack the Future coat. I use Turpenoid brand thinner for oils, and some enamels-- it's a synthetic turpentine (it might work with Humbrol, but I haven't tried it-- but it does work for sure with Model Master enamels). However, Turpenoid comes in at least three "strengths"-- I'd use the kind formulated for thinning. There's a mild one I use for tinting, and there's another one that's made for brush cleaning.
VR, Russ

You know Russ, I do agree with you on the "formulation" of Humbrol enamels. Something changed. I tried to thin with mineral spirits and the paint began to break down and clump up, hence the reason I used the Mr Color Leveling thinner.

Aha! I think so too. I was thinning with mineral spirits from Home Depot, and in the middle of a commission build, I realized the paint wasn’t drying as it should. It took three weeks for a second coat of paint to dry. I switched to lacquer thinner, because it tends to dry faster— but that didn’t help a lot—the paint felt tacky and strangely “cold” to the touch even after 72 hours of drying. I finally got it to dry in a homemade “heat box” with a 40 watt bulb, but it took several days. Next batch I used Humbrol thinner, and it worked better, but still took longer to dry than usual. So I think there’s something amuck with Humbrol paint. Frankly my favorite is Mr. Color, but it’s hard to get here in the States. Tamiya is my next “go to” paint followed by Model Master. I’m still waiting for Tamiya’s new lacquer line. And I’ve heard great things about Tru-Color paints. If only my LHS would stock them.
VR, Russ

I use something called balsamic turpentine, I think it is vegetable based (not mineral). The problem with "turpentine" or white spirit et.c is that it isn't one single well defined chemical.
My method is to test the "thinner" with a small drop of paint on a white saucer or glass with a white paper under.
Small drop of paint, add thinner. The paint should be spreading out in a thinner and thinner layer without any signs of small clumps or "clotting". If the thinner doesn't do this then use it for cleaning brushes et.c, it will not be suitable for thinning that type of paint.
Another rule is to not use a "hotter" thinner than absolutely needed since it could affect the "glue" in the paint.

/ Robin

Decades ago you could use just about any brand of thinner or mineral spirits with just about any brand of paint. Testors, Pactra and Humbrol could be thinned with thinner I got from my local ACE hardware. But in the late 80's early 90's it seemed that each needed a different thinner and that was hard to get on some of the places I was stationed. I did find out that army issue paint thinner would disolve a Dragon T-72 (with ERA). It seemed to me that every one made there own labled thinner for their paint and after many failed experiments with locally bought thinners that were too hot, didn't mix well or were too "fragrant" (I had to be considerate of the other residents in the barracks) I went with the branded ones. I kept a can of the hotter stuff just for cleanup. Maybe everyone went to proprietary formulas to boost brand sales but I could spend $50 on 5 different brands of thinners and none of them would work or $10 for a can of branded thinner that would. And when I switched to acrylics I'm following that rule just to avoid wasting money and headaches.

Thanks all for the tips and your experiences.