How do you keep your Acrylic paints Flat, Semi-gloss & Gloss?

Not all areas need to be sealed. I would not usually seal a prop and if I did it would be with a gloss coat then weatherd down to a semi gloss.

As for Acrylics coming of if not sealed.......its all in the prep and cure time. If you prep and prime your surfaces properly and then allow the paint proper cure time between coats, applying washes, decals and general weathering you should have no issues with paint coming off the actual model unless it is over handled drastically.

 This is why I usually have 3 -4 builds on the go at any given time, which are usally different subject types. I'll have an aircraft, some armour and maybe a car all on the go at the same time. I'll let painted parts sit for 3-4 days before I handle them again, while waiting those few days I just work on one of my other builds. It also helps from getting bored with a single build and single subject type.

On the down side It takes alot longer to finish a single subject that way.

Thanks Higgy for the reply. From my understanding, before you lay your decals down, it's a good idea to cover with Future or some other clear coat. If I had to put decals on a semi-gloss part that needed to be clear coated like the prop, then it would be hard to retain the original coating correct? You mention weathering down to a semi-gloss, but I'm not sure how to do that.

You have lots of options when it comes to weathering down a high gloss finsih. You can use any of the weathering powders such as Tamiyas or Mig's. You could try a wash, you can use light drybrushing of the base coat over the high gloss to bring the sheen down a bit. You could even try a wet sand with a really fine grit wet sand paper. 

Your best bet is to always try out any new technique on a scrap model or some spare parts. Check out the Armor and Aircraft sections here and when you see a finish you like ask the builder how they obtained it an go from there.

Try out some of these ideas on a scrap or ask around and let us know what worked for you! Don't get discouraged, I have spent more time in the last 6 months trying out new tecniques on scrap builds than actually building anything. Its all about what works for you and what you feel comfortable with.

Most of all don't hesitate to ask questions in peoples threads, everyone here will be more than happy to walk you through a style that works for them.