New to model building

Welcome to the forum, I have never found it necessary to wash the sprues before painting.Could be a primer thing.

welcome harleypoke to the forums. I use non concentrated dawn and I allow it to dry several hours after washing

You didn't say anything about primer.  While some folks do get along okay without priming, I personally prime just about everything. I feel painting plastic without primer is risky. I use Krylon spray can primer.

Welcome to the forum.

I try to stay with acrylic unless I want a high gloss sheen, like for a car. Most everything else is weathered which knocks down most of the gloss, I find.

Except for that pitiful little Goshawk I posted.

Steve

Welcome to the forums!  Glad to have you.

Eagle90

Welcome aboard. I've never cleaned my part before building. Might be an obvious question, but have the parts been fully rinsed off. I imagine any soap residue might effect the paint going onto the surface.

Welcome to the Forum!

I always wash the parts in dish-soapy water.  Don't usually have a problem with paint adhesion, but years ago I used to.  

For me, I think it was the thinner.  

Are you brush painting or airbrushing?  I use an airbrush, and I thin Testors paint with lacquer thinner.  Used to use Floquil's Dio-Sol, but they discontinued that.  I don't normally now have a problem with the paint lifting off.

Normally, enamel sticks pretty well since it reputedly "bites" into the plastic rather than simply lying on top of it.

Other folks here may have some other insights for you.