Newbie - Taping off ceiling corner edge help...

[0sho0]

Hi,
Trying to paint my ceiling and above a picture rail, there is an alcove(?) bit where I need to tape off the edge of the corner, and also one above a bay window, getting the tape consistently straight is feeling impossible, I can't find much online as I don't really know how to word it! Any tips appreciated, have posted pics to show where and how I have taped so far that's not really working.
TIA

 

[Wayners]

Used low tack masking tape. I think the best one is Masq Low Tack Masking.
Tesa yellow is also very good.

Why is the mask in hanging down a bit Vs stuck flat to surface?
Stick to the underside flat right on the edge with about ½mm gap to the edge.
For walls I used a £30 laser marked with a pencil. Then the low tack masking.

Tip
Run a damp cloth over masking tape prior to painting and always pull tape when emulsion is wet

 

[0sho0]

Hi, thx for reply! it's in a v shape because it's 2 separate pieces , I didn't stick it completely flat as in painting above it. I've ordered a low tack painters masking tape in bright green so I hope that will help me see the straightness of it a bit better!
I was going to paint it first with white same as original colour and then go over with the new colour to prevent paint bleed, can I skip that if I use the damp cloth instead?

 

[Wayners]

Damp cloth helps seal it but more to stop peeling.
You pull tape while paint is wet so it comes off without peeling paint on the edges

 

[endecotp]

Do you really need masking tape to paint up to that edge? Try without, maybe with a mini-roller?

 

[0sho0]

Yeah it's a rounded corner not sharp, if rather tape it off as I'm not great at painting!