Light brake pad sticking

Hello there.

I was hoping for some advice if possible please.

I got the car serviced a few months ago (Honda Accord Euro CU 2014, in US it's an Acura TSX) and the mechanic told me my front pads were on 20% and to change them. I asked if rotors needed changing too and he said that there was plenty of meat on them and long as they didn't feel warped (vibration when slowing rapidly from 60mph) then no. There was none of that and I opted to do pads myself.

Change out went fine but when pushing back the caliper pistons the fluid going back into the master cylinder was a hideous black colour so I bled the brake lines and now it's all a nice colour of DOT4 again.

However now when starting off and driving short distances I can hear a little bit of squeal from the front right wheel when driving. It goes away after about 10 minutes but then when the brakes cool down and I start off again it starts up once more. It's been a couple of weeks and I thoroughly bedded the new pads so I don't think it's that. When I move the rotor manually I can't hear anything and I can't feel any resistance. Pad backs and tabs were all greased and the shims were cleaned and regreased.

During the change out I pulled the slide pins and got as much of the old grease out of the slide boots as I could and greased them up with sil-glyde. They slide easily. This make me think it's crud on the pistons (front calipers are dual piston) that are stopping them from retracting when I take my foot off the brake, that or crap in the brake line.

What's the best way to do this? Just take the caliper off and depress the brake pedal a few times to push the piston forward, then gently slide the piston boots back off the piston and clean and sil-glyde those?

If it's blockages in the brake line I'll just take it to a brake/clutch place, I can't be bothered dealing with that.

Thankyou.