Made up a few woodies with spar-urethane finnish.How many coats would be adequate for sealing?

Several sessions should do but, spray several times within 1 hour. Wait a day. Then, sand between coats w/220 sand paper or fine steel wool befoe the next session.

Three coats, brushed on, will do fine. If you are ambitious, you can do a fourth and be really well protected.

It's been a few years since did wood. I believe I use to brush on 3 coats and then sand , then the 4 final coat. They always came out like glass.

When I first started I use to sand between each coat, then I tried after the 3 coat and add the 4 coat, it worked just as good.

On the spar urethene I've used said spray all coats within two hours.Let set for 72 hrs. if you want to sand again and spray some more coats.It says it is good enough to use within 24 hrs. but wait 72 hrs to sand again.

SU is magic IMO. Let it dry an hour or so then light sand w/steel wool. Spray again & same to get rid of any skid marks or fill holes or scratches. When near finished let sit overnight in warm room to harden. Then spray again & sand final coats. It's unbelieveable what this stuff can do.