I've had my bare 2L Spider engine block sat on an engine stand for close to a year now, without getting round to preparing it for paint. The block had been given to Stanwood Engineering in Bawtry on Guy Croft's recommendation and had gone through their ultrasonic tank. When it emerged it looked pretty much brand new. While it was there the block was bored to accept the +0.4mm Vick Auto pistons I had, and the complete bottom end will return to Stanwood in the full ness of time to be reassembled. I'll rebuild the top end myself (probably).
Anyway, first step was to mask off all the areas that don't need or want painting. I must confess, I hadn't realised what a fiddly and time-consuming task it would be. I'd also forgotten that there are 6 sides to an engine block, all of which need treatment. The block is full of machined faces to which components bolt, and these have to be protected. There are also a lot of machined circular recesses that are almost impossible to blank off using masking tape. For those I used thick cardboard, cut slightly oversize and then crimped into place using a small screwdriver.
What you see here took me over a day, and the back of the block has still not been touched. Ho-hum...

The large side closest to camera is the base of the block with all the crankcase webs covered. The side mounted to the engine stand is the clutch/gearbox end. The block had to come off the engine stand to mask that side, as it was impossible to do in situ. More delay...

This gives a better view of the fiddly nature of the masking process. The masking tape I used is cloth-based and can be quite fairly accurately with a sharp Stanley blade.

And this view shows the top deck all masked up, and the copious use of CAD (cardboard-aided design) in blanking off parts that must remain paint-free. Hopefully the next set of photos will show the masking complete and 2K epoxy primer applied.
Sometime this year, would be nice...