Carpentry and Woodworking - Poly questions

I used a oil pased poly applied with white chinese bristle brush and lightly sanded in between coats with 220 sandpaper. I also wiped off the mouldings with a tack cloth after sanding before applying another coat.. I am still getting little bumps in the poly. It almost seems like the first coat was smoother then the subsequent coats. Any tips?

Two things. This is either grit in the finish or air bubbles trapped in the finish. Straining the finish will help eliminate the first. Not shaking the product and not overbrushing the finish will help eliminate the second.

Thanks for the response. I think I have narrowed down my problem with the grit due to not cleaning my brushes thoroughly. A new problem seems to be developing though. I am using minwax oil based poly in a satin finish. I have noticed some spots on my mouldings look like they have semi-gloss and are not smooth. This is a quick dry poly. Should I thin it down a bit with mineral spirits. Will this correct my problem. Best way to strain poly? Would a coffee filter due. Thanks for any suggestions.

If there is a difference in gloss between spots, it may be due to differences in brushing. If this is not an initial coat. Maybe a bit thin in spots.

Straining paint or poly: you can buy a strainer at a paint store for $1, old panty hose will do; somewht finer than a paint strainer. Coffee filter too fine, it filters water.

Not cleaning up will do it.

Ordinarily, thinning is done for initial coats to enhance settling into the grain. I doubt it will matter much on top of a full strength coat. With poly, lay it on, and tip it off.